If you wish to recruit people to be extras/background in a film, I suggest you try advertising on Starnow, or any of the other similar broadcast industry sites.
That isn't a bitchy comment at all, that is genuine advice, and you will probably get people falling over themselves to get a "break" in such a big name company.
HOWEVER. I may have misread your OP and you might be recruiting for a filmed gang-bang. In which case you need to clarify, both on here and anywhere else you are trying to recruit.