I have used this style of creating and modifying textures in my personal work for years , here: Jonathan Arias
I bought Von Glitschka books in college in 2009 and doing this style of texture applications is just amazing. after a while you will want to make your own textures. Which just involves making an image into black and white, adjust the levels and make a tiff. than place that tiff as a layer mask into the shape in illustrator and adjust to your hearts content. You can repeat the same texture as many time within the mask and do blending modes to achieve blends and fades as much as you want.
I found this to be way faster than going back and forth with brushes.