Let me be sure I have the concept correct, The node tree you're building for Snow's skin is like a handy palette of all the colors you are going to be using on the skin so you don't have to jump all over the place picking material colors. Just establish each shade, list them in one spot in the Vertex Groups, and pick from there, cutting down a lot of jumping around. The node trees look intimidating at first but actually are cutting out a lot of repetition of steps.