Here is a personal piece that I worked on during a couple weeks that I took off work. I wanted to stay sharp, and also I wanted to play with my new copy of Autodesk's Sketchbook Pro! Below is the finished piece and some work-in-progress stages.
Final. Light and dark tones added. The dark tones I added by painting different shades at full opacity. After doing so I realized that, even though this is something I'm doing for fun, I would have preferred to use just black on a semi-transparent layer. That's exactly what I did for the highlights (not using black, though... naturally) and I enjoyed that much more than hand-picking several different shades.
WIP #4. Base. I put down a base coat for all of the colours that I would work with. I put all of the base colours on one layer; since this was a personal project I didn't want to have to navigate through several different layers. Not if I didn't have to. The paint splotch however was its own layer. I used one of the pre-made brush designs as a starting point, but scaling it up this far made it extremely blurry, so I painted over most of it and just had fun designing an energetic splat!
WIP #3. Line Weight. After putting down all of the clean up lines, I went through and added more weight to some carefully selected areas.
WIP #2. Clean-up. After I was happy with the semi-rough I proceeded to create a clean version on a new layer. Looks like I jumped ahead and began adding some heavier lines before remembering to save a new version.
WIP #1. Semi Rough. After scanning the rough draft from my sketchbook I did a lot of plussing and re-constructing on a new layer inside Sketchbook.
Rough Draft. After a couple pages of brainstorming, this idea appealed to me with its energy and simplicity of design.