I was very lucky to work as a Digital Compositor in my first Hollywood movie: The Gambler, starring Mark Wahlberg, Jessica Lange and John Goodman, and directed by Rupert Wyatt.
I worked 5 weeks on it, most of the time integrating some CG spectators with the real footage of a basketball game and later doing some retouching and adjustments in a couple of shots at a Casino.
The Visual Effects were done by Atomic Arts and the program used was Nuke.