Make sure, obviously, your prep work is good. The better it is, the better the turnout.
I just painted my square, I used a new paint called Ful-Thane, its sort of like an emron, a marine paint. It has a reducer and a hardner that also comes with the paint.
I also used a featherfil paint, which is a thin primer like paint that fills tiny holes. You then sand it smooth with 320 dry and lay on your primer, then your color.
I actually did featherfil/sealer/paint. The featherfil acts as a primer, sealer helps to seal it, obviously.
Try and find a wax and grease remover as well. SPray it on your ski, wipe it off, and use a 2nd rag to dry it. It removes garbage and dirt and grease etc. from your hands, and anything else that touches it. But, you shouldnt touch it after you wipe it down. Its not THAT important, but it cant hurt!