I spent all day (seriously, all day) detailing my car, and I gotta say there is no other vehicle out there that is more difficult to detail! Let me explain: vehicles with large, flat panels are easy to wash and wax. It's the angles, edges, and small panels that take forever to get clean and protected, and the 2011-14 cars have more creases, scoops, and lines than some Pikes Peak racers. My last car was a 1995 3000GT. The beautiful curves of that car made it a breeze to detail. The chiseled look of the WRX is menacing, but man does it make for an arduous process to wax.
Everyone knows wax is going to hurt, no matter where you're having it done on your body. Have you considered laser hair removal for your butt instead?