Alright. Now we're back on track. I blocked in the shadows with solid black. Most of that will not stay solid black, but it helps inform me of light source and how the light affects each material/surface. Knowing how reflective a surface is plays an important role in all this. This is why the best artists will use heavy reference to study how the light plays on each type of surface.
As I went through the shadows I sampled a few places to see how I might want to handle the texture as I get to it. I also took note of some things that were not quite working for me. This is my last chance to make some structural changes before hitting a point of no (easy) return.