Their sessions are two hours and cost $85 a guest, which includes Champagne, snacks, a teacher, a waiter, a model and a group photo shoot. Rules prohibit guests from touching the model and photographing him while he’s naked.

Jess Cohen, 28, hired the Artful Bachelorette for her best friend’s bachelorette party. The guests, who were flying in to New York from around the globe, ranged in age from 26 to 75. She made the choice after dismissing options at both sides of the spectrum of decorum, like strip clubs and afternoon tea. “This was the perfect balance of fun, sexiness and creativity,” said Ms. Cohen, a producer of film and video based in Williamsburg, Brooklyn. She admitted that the bride was apprehensive when she walked in and saw a topless waiter. “She said, ‘My grandmother’s here,’ ” Ms. Cohen said. “But after 5 or 10 minutes, everyone was laughing and enjoying it.”

Cara Eisenpress is another satisfied customer. “People are into doing exercise classes together, but I’m not into exercise classes,” said Ms. Eisenpress, 28, a food writer in Prospect Heights, Brooklyn, who was surprised with an Artful Bachelorette party last fall. “I was very resistant to a stripper, and I don’t love to be the center of attention. I had done a bunch of drawing in high school and college. It was nice to be part of the audience, sitting there with paper and charcoal. It was down to earth with some raciness.”

Back at Ms. Albright’s party, it was time to take out pencils. “Without further ado, this is the lovely Kurt,” said Ms. Childs, introducing the model, Kurt McVey, 28, a former lacrosse player with styled hair and chiseled features. Ms. Albright was asked to remove Mr. McVey’s towel and she did as she was told, though she looked terrified. There were schoolgirl giggles from the crowd.

Ms. Childs, who has a fine arts degree from the University of New South Wales, called out instructions: “Stick figures are fine at first. No crossing anything out. No erasers. The more you drink, the better you draw.” She guided the group through six 60-second poses, among them facing front, facing the wall, one leg on a stool and archer pose. A final word of advice: “Don’t forget to draw the male member! It’s very important.”