I Demonstrated for the Illinois Watercolor Society in June, where I splashed paint on my Steam engine with a #16 brush to simulate rust and peeling paint. i did it small first before the demo to make sure it would work (11"x16"). I then demonstrated on a full sheet (22" x 30"). Here is the small one, the Demo and the finished peice (they look quite similar).
I have a 6 page article in the Art of Watercolor magazine from in the 16th issue (October-November 2014). Here is a PDF. It's fun to be in a magazine, and there is a lot of other good work in it as well. I use a lot of drafting tape and toothbrush in my work, I tried to show an example of how I use it in thew article. I always forget to mention I learned the technique from Alain Gavin, who teaches in Evanston, IL.