I’m extremely familiar with the Blender Internal materials, but I’m only now starting to learn Cycles. It took me longer than I thought to work out how to use one texture as the distribution (stencil) for another, but I finally figured it out so I wrote a short tutorial. It includes a few other absolute basics like setting up bump maps and organising nodes, so hopefully it will help explain the basic workflow. Maybe this isn’t of much use to anyone but me, but just in case there are others out there in the same situation, here it is :