This is really cool, your lines are so clean and solid. I would look for another brush for that BG paint though, it's too blurry/pixelated. Don't know if you ever tried but if you scan a patch of paint (or look for images online) you can use it as a texture for your own brush.
thats the effect i was going for. its in the natural brushes 2 pack. i made the brush size around 1000 to create that. it was just something i was experimenting with.