What's the best way to sand and spray paint particle board?
Trying to make replacement bases for my floor-standing speakers. The originals were made out of particle board and appear to have a black spray-paint finish. They were destroyed in the post when the person sending me the speakers failed to package them properly. I now have the particle board cut to the right shape and I have begun the process of sanding. It is my intention to spray a primer on, sand, spray a top coat, and then spray some sort of finish. so here are my questions:
(1) I have sanded the board down with successively finer sandpaper and finished with 1500 grit wet and dry. This is a very smooth finish until you wipe away the dust at which point it becomes rough-ish again. Having done a bit of research I am now concerned that I have sanded the board down a bit to much, some forums suggest taking the board down only as far as 250 grit before spraying on the primer. What should be my finishing grit before spraying on the primer? My assumption was the finer the better but I'm not too sure now. If the finish should be fine then how do I remove those stubborn fibers?
(2) what type of spray primer works best with particle board? There seems to be a multitude but most of the information related to car/auto body work.
(3) what grit of paper should I use on the primer?
(4) what should I use as a top coat?
Much thanks in advance