“I feel very much like I’m being welcomed into a circle of excellence,” said Daphne Always, a cabaret performer, model, and musician, before disrobing and stepping gracefully onto a crate. She had been invited by the painter Will Cotton to pose for one of his figure-drawing sessions, which he was hosting en plein air on the roof of Ryan McGinness’s Soho studio. Gathered around as always were a bunch of New York artists — the youngest in their early 20s, the eldest in their 60s — working in a range of styles and mediums.