Well they can have multiple maps, but it seems that bodypaint gets confused if the uv maps overlap, even if they aren't on the same material to be painted.

Al the tutorials I've seen have somethng already loaded, and they go through the wizard, or uv map from ground zero, and that's not what you really want to do.. you just want to use the existing uvs, and paint.

Way too many people take way too many things way too seriously.