If the slime material doesn't have relief, I would rather go with a texture map. 3 or 4 hires images containing an alpha channel (white with a big black dot) that you put as textures and that you scale to progressively cover the whole hand.
Does this make any sense?
If you're slime has relief, well obviously the meta clay seems an excellent choice.
Hope this helps
Salutations - Cheers
Bernard Lebel