A Couple days ago I spent some money on a new tutorial from The Adamation Station store. If you don't know who this guy is, I highly recommend watching his free tutorial Voodoo Doll. I had never seen before this type of work-flow. Adam is drawing as 3D renderer diffuse, reflection, subsurface scattering passes and compositing them together. For me, Old Mother Yew was a perfect match because it covered an area of knowledge which I lacked.
There is one of the exercises which I did while watching Adam Duff's tutorial.
From this tutorial, I also learned about Daarken. His free tutorials about “Brush Controls” and “Creating Custom Brushes” were a perfect extension of the knowledge which I got from “Old Mother Yew”.