How does one become a research consultant for Hollywood films?

I'm interested in doing research for films, especially historical pieces, like Braveheart or Shakespeare in Love, but not sure where to go for this information. Can anyone help? Do you know the names of any organizations or major research firms that do this type of work?How does one become a research consultant for Hollywood films?I think for this purpose its not that people go to hollywood but actually Hollywood people go to different experts and ask them to do research for them. I guess if you become story writer or Director than you can do such movies.