MadMax is right, Smelly-Skelly.
I did that very thing (rubber gloves and Great Stuff) for my first hands. Well, it did work, but it did tend to come out the bottom when it expanded. And out the sides, the fingers, etc.
Looks gross, so while I couldn't use it for hands I did stick them on the ground for the heck of it.
The first set of somewhat usable hands I made were with Great Stuff and welding wire. I made a mold of aluminum foil, sprayed the foam in, and laid the welding wire in after it set up a little. Those came out fairly good, and the fingers could be easily bent to shape.
The sandcasting idea is probably the best. But if you want quick and dirty, even just spraying Great Stuff on wax paper in the shape of a hand will do the trick.