I've been searching but really haven't found much on working with Transparency when painting beyond this posting:   http://3dcoat.com/forum/index.php?showtopic=18649&p=129547   The problem with this is being able to perform the erasure across multiple layers at once. It doesn't appear that 3DC has have a means of using a layer as a transp mask in other words, but maybe it does and just not an apparent process. I'm still pretty new to using it.   Would doing this be better within the en