Marshall McLuhan called advertising the greatest art form of the 20th century. In “No,” Pablo Larraín’s sly, smart, fictionalized tale about the art of the sell during a fraught period in Chilean history, advertising isn’t only an art; it’s also a way of life. That’s certainly true for the young adman, Rene Saavedra (Gael García Bernal), who skateboards through the movie, pausing now and again to care for his son or dash off another ad campaign. When approached to help create one to oust Gen. Augusto Pinochet, he signs on. Rene may be vaguely interested in selling the country on life without Pinochet, but what reels him in is the challenge of pitching a superior product.