Here's a character design for a story I did with writer Sara Ryan. The comic was part of the Comic Book Tattoo anthology that came out a couple years ago. I've always liked rough watercolor fills- I'm doing my best to replicate them in a digital process.
A while back I had a job for the Addams Family Broadway Musical where I needed to precisely emulate a Charles Addams cartoon in a digital, multi-layered format. In the process, I discovered the wonderful Nagel series brushes for Photoshop... They do a good job of emulating natural watercolor washes. Here's one of the more splattery examples:
...And here's the original Addams cartoon, plus my hi-res, all-digital copy. The original here isn't the copy I worked off of, so the contrast levels differ, but it's still fairly close:
So there's my first counterfeit job, approved by the Charles Addams estate itself!
Definitely give the Nagel series brushes a spin if you're looking to emulate real world watercolor effects. They're free, there's lots of them to try out, and it saves you the time of engineering your own brushes from scratch (which is admittedly fun too).