This is a quick demo of REAL WATERCOLORS FOR Ai's capabilities. I was asked how to create a watercolor fill effect. I've used the solid vector version (top) and the 10-color vector version (bottom) for this effect. The rest is masking magic. You'll find everything you need in the demo!
This one is another approach on texturing strokes. The PENCIL-WITH-A-PENCIL is not really exactly brush - its a versatile texture stamp. I've created a just tiny repeating pattern (lead on paper/scanning/post processing/create seamless) hence we use it as a stroke. The upside is that the outcome looks exactly like the desired texture with the applied brush dynamics. The downside is that -because you basically apply a texture- you are bound to the color of the texture. In this case it makes sense but I won't work with all media styles. Well, just try it out.