I wouldn't recommend waxing your top sheet before you paint it as the paint won't bond very well and the wax will eventually come off with the paint on top of it...
If i where to paint the top of my board i would probably sand the entire area you want to paint just enough to rough it up`so the paint will stick better. Then paint the area with a primer sealer and let it dry for around a day. Then paint your design or just solid color on and let that dry then finish it off with a clear coat to add some shine and protect the paint.
2011 Ride DH2 159 Wide - 2009 Burton Missions
2009 Burton Bullet 160 Wide
Riding Days: 81