I've been working with the free Susan character, and I wanted to change her hair. As far as I can tell, I can make her current hair invisible and put another hair on top of it, but I can't remove it? 
And when I want to change an item on a character, like going back to change the skin after I've added a detail, it doesn't give me the option to remove a layer, it just adds another layer on top of it. This builds up to a lot of layers. How can I fix this?