vaseline for both of them
I did a little experiment last night (because I lost the tutorial) and it seemes to work great. I took the white silicone and my caulking gun and spread a thin layer of vaseline on a foam hand I got from a Bog of Bones at Big Lots last year. I put dab of silicone on a gloved finger and pressed it into the cracks of the hand. After the cracks were filled, I ran a thin layer of silicone over the entire thing, making sure everything was covered. I peeled it off this morning and if held it's shape while remaining flexible. Today I will try to do an entire skull and then do the plaster mother mold tomorrow. I will upload pics so you guys can see what it looks like. If anyone can find the original tutorial, can you please post a link here?