You arn't likely to get a fantastic finish with spray paint as your top coat. "behind every show room finish is a good buffer " What might have worked for you if you are going the spray can route is automotive acrylic. Once you have primed you can sand the primer smooth to provide a nice smooth flat surface for base coat. Then you can spray several coats of acrylic clear. With enough coats of clear you can sand that perfectly smooth and then buff and polish to a flat, smooth gloss.

Funny you should mention the screws being too short, I could swear I have read another post here somewhere with a similar complaint. I havn't checked mine to see, as I am awaiting (if they ever manage to make it onto a plane) better pickups that are according to specs, thinner. I'll be bedding them with high density foam rather than bothering with the springs.