I put these lessons together in 2010-11. If you're old enough, you may find the UI nostalgic. Even though the software has evolved significantly since this was completed, the embedded lessons still provide those looking at digital sketching with a roadmap and some specific techniques that will prove helpful.
Watch the first video for an overview. These lessons walk the viewer through how to utilize the power of digital to generate exploratory sketches, refine line-work, render with color, create custom brushes, and provide some context.