I’ve barely got my coat off before Betty Dodson, the New York sex educator, sets precisely the frank, ribald tone she has become renowned for. Dodson is 90, but has, I tell her truthfully, the skin of a woman at least 30 years younger. “Well,” she declares, matter-of-factly, “I smoke and I drink and I masturbate. I’m a hopeless masturbator.

“Nobody factors in pleasure for health,” she continues. “But if you’re not having fun, you’re not going to be healthy.” Quite.

Dodson began her radical BodySex classes, in which she teaches women to masturbate to orgasm, in the early 1970s — the weekend-long courses, for up to 20 women at a time, were held here in her midtown Manhattan apartment for more than a decade before the HIV and Aids crisis curtailed sexual freedoms and Dodson branched out into writing books, including the bestselling Sex for One, which earned her the title of “godmother of masturbation”.

Since 2015, with the help of her protégée, the 46-year-old former corporate lawyer Carlin Ross, Dodson has resumed the regular workshops, and she estimates that she has helped close to 10,000 women to break through the barriers of shame, negative body image and anxiety about sex and masturbation.

The bestselling Sex for One earned her the title of “godmother of masturbation.”

And now she has a new, millennial audience of millions, thanks to her appearance in an episode of the Netflix series The Goop Lab, alongside Gwyneth Paltrow, the chief executive of Goop and the patron saint of vagina-based luxury products — jade eggs to “increase sexual energy”, mugwort vaginal steam treatments “to balance female hormone levels”, and, latterly, a $74 candle called “This Smells Like my Vagina”.

“It’s our favourite subject: vaginas!” cries a beaming, glossy Paltrow in the episode entitled The Pleasure is Ours before being swiftly admonished for her gynaecological geography by Dodson, who tells her the vagina is actually just the birth canal; she wants to be talking about the vulva. “Vulva, vulva, vulva,” her diligent student Paltrow repeats.

Like any assiduous journalist, I’m big on research, getting to know someone as well as possible on paper before meeting them in person. But Carlin Ross is the first interviewee whose vulva I’ve seen in close-up before looking her in the eye: The Goop Lab features Ross demonstrating the “genital show-and-tell” that makes up part of the BodySex workshops.

In fact, I’m slightly surprised, when I arrive at Dodson’s one-bedroom, rent-controlled apartment, where she has lived since the 1960s, to find Ross fully clothed. For the workshops — which are still conducted here, all without clothing — she answers the door to greet everyone naked.

The Goop Lab features Ross demonstrating the “genital show-and-tell.”

Excruciating though all this may sound, Dodson and Ross have a waiting list of hundreds and are adding ever more workshops to their schedule this spring, such is the overwhelming demand for naked orgasmic instruction, at about $1,200 a throw.

I find Dodson in her bedroom-cum-study in a dressing gown, smoking a Marlboro Light. While her speech remains as wonderfully salty as a sailor’s, Dodson is losing her hearing, and my English accent doesn’t help, so there’s a lot of translating through Ross. Other senses remain undimmed, however; when I sit beside her, she inhales deeply and tells me that she loves the way I smell. I’m flattered, and also a tiny bit unnerved.

On the desk between us are three packets of cigarettes, a half-eaten muffin and a collection of marijuana chocolates, and on the floor by my feet in a wicker basket — the sort more commonly used to display pine cones or pot pourri — is a nest of Hitachi Magic Wand vibrators with the proportions of power tools. “You want ’em big,” Dodson says when I comment on their unusually substantial size. “So you don’t get carpal tunnel.” Ross’s four-year-old son, Grayson, then wanders in from the lounge clutching a large, spiky rubber dildo, and inquiring as to its purpose.

In a series that can otherwise feel eye-rollingly self-indulgent (Paltrow claims in one episode that “being the person people perceive me to be is inherently traumatic”) the episode featuring Dodson and Ross seems genuinely subversive.

A nest of Hitachi Magic Wand vibrators with the proportions of power tools.

Not only for the gallery of vulvas shown (“dicks are everywhere — in museums, in sculptures, dick pics — but you never see women’s vulvas,” Ross reasons) and her own on-screen orgasm (she admits to throwing back some tequila in advance of this), but also the infectiously empowering effect of witnessing women getting comfortable with their own bodies and sexuality, sometimes for the first time. And it’s gratifying to watch the woke, beatific Paltrow blush when Dodson pronounces the mainstay of her sex advice to women: “Get on top, and run the f***.”

Dodson grew up in Wichita, Kansas, and moved to New York at 19 years old to work as a fashion illustrator before finding her way into making feminist art. She married at 29, divorced six years later and had her sexual awakening at the age of 37, thanks to Grant Taylor, a 42-year-old English professor and the first man to enthusiastically give her oral sex, with the lights on, and who also reassured her that her labia were not deformed, as she had always feared.

In the early 1970s she began hosting sex parties at the apartment and noticed that “the men were always having a great time and the women were not — they were faking it; it was a crock of shit”. When the women found their way to Dodson’s bedroom, however, they would use vibrators and stop pretending.

From those casual, organic, orgiastic groupings grew the idea for the BodySex workshops, which she sees as “totally” a feminist act, although different from those of other, contemporary “very conservative” feminists, such as her old friend Gloria Steinem. “It was all, ‘We want change, but we don’t want to upset anyone, we don’t want to rock the boat too much.’ Dodson sighs. “You’ve just gotta go out there and make a mess.”

Today the workshops are little different from those early iterations. Everyone arrives and immediately disrobes. “Sometimes they are visibly shaking,” Ross says. “But by day two that’s all melted away and they love being naked. It sets you free. And nobody has ever walked out or refused to get naked.”

Then, Ross and Dodson ask everyone how they feel about their bodies and their orgasms. “No one feels good,” Ross says. “And the better-looking the woman, the more hang-ups.” This is intriguing to me. “Yes, the larger women usually feel great,” she says. “They’ll be, like, ‘Yeah, I could lose some weight, but I’m good.’ ”

During genital show-and-tell, everyone takes a turn to examine her own vulva in a mirror and display it to the group. “No one goes, ‘Oh, that’s an ugly pussy’ — everyone finds something beautiful to say,” Dodson says. “And that’s the real bonding moment.”

From those casual, organic, orgiastic groupings grew the idea for the BodySex workshops.

On day two, in “erotic recess”, Dodson and Ross demonstrate the former’s “rock’n’roll” technique, which involves inserting a steel barbell (available online for $138) into the vagina and squeezing the pelvic floor muscles, while using the Hitachi power-tool for clitoral stimulation. The class then follows suit. “We make it very clear that you do not
have to have an orgasm,” Dodson says. “But everyone does.”

Translating the technique to partner sex simply involves swapping the barbell for a penis — “it all translates”, Ross says. But, Dodson says, she advises women, always: “Control your own clitoral stimulation.”

Participants range from women in their twenties to their eighties, and these days they fly in from as far away as China and New Zealand to take the cult class. Ross and Dodson have also trained 20 women to coach BodySex classes in other countries, including Spain and Iceland, and, much to Ross’s excitement, now have interest from a woman keen to coach classes in India.

Since Dodson began working in the field almost 50 years ago, others have entered the fray: Joseph Kramer founded the Body Electric School and the Orgasmic Yoga Institute in Oakland, California; Reid Mihalko runs classes in “High Performance Relationship Mastery” as well as sexual self-confidence; Jaiya Ma offers private erotic coaching; and the former porn star Jessica Drake has set herself up as a sex educator and orgasm coach.

Possibly unsurprisingly, almost all practitioners are generally based in California, with Australia also supporting an active sex coaching community. Until just over a year ago, OM (orgasmic meditation) classes — in which one person strokes another’s clitoris for 15 minutes — were available in the UK too, but are no longer offered anywhere in the country.

While the specifics of the techniques vary, most are focused on women. Does Dodson coach men?

She advises women, always: “Control your own clitoral stimulation.”

“I have, but it’s too much trouble,” she says, waving a hand in the air dismissively. “They’re so resistant. They’re the ones that are supposed to know everything and run the f***, so it’s very hard for them to bottom [become the receiver/less dominant partner during sex].”

But the rampant proliferation of porn has, Dodson and Ross agree, also created unforeseen problems in male sexual function. “We get a lot of young men who write into the website, saying, ‘I know porn isn’t good for me, I know it’s messed me up,’ and they can’t ejaculate in a vagina,” Ross says.

She tells me about a researcher friend who was trying to put together a study about the effects of porn on men aged 18 to 24, but couldn’t find any who had never watched porn to act as the control group. But she understands the problem. “Men are programmed for variety, and porn offers infinite variety.”

Dodson, who never married again, also believes in variety, and holds a sceptical view of monogamy. “I’ve never been able to be monogamous for too long,” she says with a shrug. “It looks to me like everybody ends up cheating at some point.”

Long-term monogamy and good sex are, in her view, “improbable, but possible”. If the sexual spark has gone, Ross recommends taking a workshop — or sending your partner on one. “It’s all about dopamine, and new experiences are a way to create more dopamine — that’s why holiday sex is hot.”

As I prepare to leave, Ross says I should come back for a workshop sometime. I’m not sure I’m entirely ready for genital show-and-tell, but I relate to them the time I went to Sex Camp in Australia and spent the most challenging 90 minutes of my life in a class called Naked Awakening.

Dodson stands up, and I think she’s going to hug me for my efforts, but instead she cackles, asks “Like this?” and throws her dressing gown wide open to flash me.