I've updated my sketchbook. Since I'm way too lazy to post it all here AND on my conceptart.org thread, you'll have to go there to view it. Plus, I'm not sure how some of you would react to full frontal nudity. I know, try to contain yourselves....
So, this one is just a simple rock shape that I painted for my brush tip shape. See the previous tutorial below for how to save out a new brush shape.
Next, I set my settings as shown below. Sometimes while I'm using the brush, I may want a slightly different effect, like more spacing or scattering. These adjustments are easy to make once you understand what each setting does.
This speed painting I did a little while ago was done it about 20 minutes with my Rock brush and a flat version of the brush shown in my previous tutorial.