I am nearly there but find myself having fits on layering/compositing and just wind up chromakeying to get the result. I am sure that Vegas can do with compositing (there are so many modes)
Have you looked at the Parenting tutorials on the VASST site? or the tute's on difference masking from either Matt Chaboud or myself? Or the several masking tutes on the VASST site?
Do a search in the search tool for masking, you'll find a bunch of tutes. On just how to use each mode, or each individual mode, that would constitute a book all by itself, which is why I've just written what I can when time permits. Maybe someone else out there has something, but I've not seen anything more available.