I have made many of these because they really get a good reaction from people. I hung them on skin stretching in my troll area a few years back and I started making them for my Dante's infero house in...2002.
I will give you the non latex way first. then the way Ive done them with latex available.
I stand a piece of plywood up on its end so I have a verticle table.
I then staple clear or black bags (about 2 or 3mil) to the plywood in the rough shape of a person (If your hanging them upside down when finished then staple the arms above the head.
Wad up one bag for the head and six or seven for the torso. one bag for each arm and two for each leg. Just wad them into the rights silouette of a person.
Then with a heat gun on high hit the plastic, it will wither and shrivel and harden a bit (but still stay flexible). You will get very organic textures and will me able to melt the bags together to be one skin. With practice you can get fingers and even toes on your skin.
If you used a black bag then its often enough to just drybrush the skin with flesh colored latex house paint on the skin side and a blood colored (I like bear China red) latex house paint on the skin side.
A clear bag you would paint with the flesh then water down some brown paint and antique it. on the "inside" of the skin you can just use the red again and the clearness actually takes on a gristle type quality and looks really good.
You can add hair weave hair (I get mine at a beauty supply store for $.99) to the head with spray adhesive. Layer it the way hair falls start at the base of the head and work up layer by layer.
Then your done!
If you have access to latex then here is an alternate methood.
On a large piece of plexiglass, or mirror ,( Or a saranwrapped sheet of plywood) or any plastic really-
Use masking tape to make the outline of a person.
paint latex inside the tape , before it dries peel up the tape leaving a nice crisp edge, then let it dry. then do layer of latex and tissue paper over top of that. attempt to stay within the lines.
then let that dry.
then paint ith the flesh and peel and flip it when that dries. On the skin side I like to give it alot of nasty texture with clumpy latex and tissue paper whereas on the other side I try to keep it fairly smooth. Paint the insie red then dor hair and your done.
I hope this helped you out or inspired to try it yourself. Im sure there are tons of ways of doing them but the plastic works great for me and is super cheap.