Trying to ape Shepard Fairey. Still not right, but closer than this one. I think I need to give up on the automatic edges by compressing the layers trick (as done in this method of sketch fakery) and just trace edges manually.
I started with this tutorial, but the only thing I've really kept from it is the colors and the use of threshold layers. No use of illustrator; this is purely photoshop (but I would use illustrator if I was needed one that I could enlarge).
In case you care: the base picture.