how does a woman go about becoming part/body double model for movies and TV? Is there a particular agency who handles  such models? Or several agencies?

In the last two weeks I've been asked about this twice. Both women are figure models, and are fine with movies/TV style nudity.

I hope some of you ladies are working as body doubles, and can share some wisdom for me to pass on to these two ladies and future ladies who ask about the same work.

Thank you in advance for your wisdom.