In our EZ Hand Casting Kit we include a small bag of plasticine clay for putting behind long fingernails. Doing this (artfully) makes the fingernails a bit thicker in the hand cast so they don't break off when you're unmolding and throughout years of handling. This can really make your life a lot easier. This bag is enough to do two hands with very long fingernails.

It is also used to plug the nose holes in a face cast prior to pouring in the LiquiStone.