
Rex R. answered 05/04/19
Writer, public speaker, and visual storyteller
Place the main subject(s) in the background, and stack the other actors closer to the lens. The idea is to give the impression that there are so many people that there's no way to get a clear shot of anyone. Have someone cross in front of the camera from time to time. You can enhance the feeling of a larger party by adding chatter and party music in post.