Also, shake the heck out of it, regularly (before your paint and while you are spraying).
Maybe someone will post a link to a recent post showing a home-made spray-can shaker. I wish I had seen it before I painted my heater with the Rustoleum Hammertone spray-can paint.
The shaker that comes to mind is a hose clamp on an old sawzall blade... low tech but effective.
