They say that those who can’t do, teach. And those who can’t teach, teach gym. But sometimes, those who can do also teach, and if you’ve made 70 movies over 20 years, while raking in a bunch of Independent Spirit award and Oscar nominations, apparently it’s time to share some of the expertise. Christine Vachon, whose films as a producer include “Boys Don’t Cry,” “Hedwig and the Angry Inch,” “Happiness,” “One-Hour Photo,” “Kids,” “I Shot Andy Warhol,” “At Any Price” and virtually All the films of Todd Haynes, has joined the faculty of Stony Brook Southampton Arts on Long Island. As part of the Stony Brook Film Festival, which begins today, she’ll will get a lifetime achievement award on July 26, which will coincide with a screening of her latest project, “Deep Powder,” a drug-smuggling drama set in the ‘80s, directed by Mo Ogrodnik and starring Haley Bennett and Shiloh Fernandez.