Audience reaction videos are common in Hollywood film advertising, but you rarely see them for indie films. With a little bit of preparation, however, you can use an enthusiastic audience fresh from a screening to build buzz for your film.
It seems to be working for my clients Joke & Biagio, who made Dying to Do Letterman – after their sold-out screenings at Cinequest they went on to win the audience award at that festival. Then they did it again at the Cleveland Film Fest. I hear they have more festival screenings on the way.