i like the bird flipping idea. the best way to do that would be to buy some algenate(same stuff they put in your mouth when you get braces) it cures way fast, wont burn you like plaster will, and it relases off your skin easy. you then pour plaster into the algenate mold. pull out the plaster sand ,prime, clear the plaster and bam you have a rad looking master to build the silicone mold around. just incase you are thinking about the dildo light or maybe just a regular dildo you can do it this way too haha!
as for just sticking your hand in the silicone... if you want to hang out for 24hours you could do that but i have no idea if that pam will give you inhibitions. silicone is very sensative to chemicals when it is in its liquid state.
for the guy asking about the plaster mold, if it doesnt have any under cuts you can do a mold that way but your mold probably wont last more then one cast. but if you only want one part and you want it to have under cuts, sculpt your part in wax. pour the plaster on, when it is cured, melt the wax out, cast the resin, bust the mold off, sand and finish the part as needed, maybe hit it with a bead blaster(use glass beads not sand if you are making a lens) then clear coat it.
oh on the pigment make sure not to go over 3% of your ratio or you may run into curing issues
as for the foam, use high density foam unless you just want to rough it out in medium and then cover it with bondo. it is really dense, most people think it is some sort of wood. the high density foam we use is called pro-lab. there are tons of names for it: ren-board, ren shape, butter board.
we get it from t.m.i. here in slc i am sure you can find some where local for your area.