Skin: the final layer

Skin is the final layer of my anatomist's head.  In the photo up top I'm half way through applying skin.  As in, I've literally applied it to half the face so you can see what it looks like before and after.  Here's another photo:

It reminds me of Batman with the two little horns and the skin peeled away from the mouth area, so I think I'll call it Bruce.

I want to have the skin peeling away from the skull, which is already finished at this point and is quite a different colour to what the skin will be.  That's why, if you look at the left side of the face, you can see the edge of the skin already painted.  That's actually the bottom layer of skin, made from coloured paper.  The top layer is what you see on the right hand side.  By doing it this way, I don't need to try and get a paintbrush in between the skull and the underside of the skin, and there's no chance of getting paint anywhere it doesn't belong.  

The skin on old specimens like this tends to be quite dry and mummified, so that's the look I've gone for.