Clear coat: bad idea

So, tonight I decided to go and start over the chalk board. I took the car up to the carwash and started blasting away the lovely artwork. Unfortunately, by the time I got to the hood, the clearcoat which had the blackboard paint on it, decided to chip away. Pretty bad actually. Almost the entire hood was turquise again! SO I got it home and lightly sanded the entire car to get any remaining clear coat that was chipping off, and to roughen the surface. I bought two cans of primer and primed the entire car. I will respray the blackboard paint tomorrow and see how that stays on. I did find that instead of just blasting it, the foamy brush at the car wash works almost better and is far less harsh on the paint. So, lesson to those who may follow my footsteps, prep the area, primer, and multiple coats of BB paint.