Ok, I need to find some GOOD case paint

problem: The spray paint I used (Krylon) hardly procects andthing on my case, I could take the paint off with my fingernail if I wanted.

I sanded down all the little bumps on my case before I painted, cleaned it, then put on spray paint primer that is made for aluminum. Let that coat dry, sanded it, did the same thing, sanded it. Then put on 3 light coats of the krylon, and that's where I am at. The krylon paint hardly sticks to the primer. So what kind of paint should I use this time?

Also, any recommendations of a good clear coat?