A lot of this relies on typing words, duplicating, formatting and moving those around to rebuild the light-and-dark areas of the image. Very much the same as in Photoshop. I wouldn't use brushes for that. But if you want to, take a look at scatter brsuhes. Then you need clipping masks. You need to posterize the photo and create vector versions of these. Although there are methods for doing it automatically, you will most probably get better results doing this manually. If you want to try tha automatic way: Live trace. Then puzzle all these methods togther. You might even find tutorials. Maybe here: I haven't looked through all of them: http://psdcollector.blogspot.com/2010/04/100-examples-of-typography-portraits.html
... View more