Very good info. All the casting shops I've been to said you can't use caulking because it's too thick and holds air bubbles and that Great Stuff foam doesn't work. I guess they want me to spend top dollar for their products.
I'm going to try your way. I know the Great Stuff foam needs air and takes a long time to cure and is hard to work with. Is there an additive to speed up the curing of the foam like the caulking?
(The shops here charge about $700.00 to cast a set of foam hands)