If you are using urethanes you need - primer ( epoxy=moister resistant. or Poly if not need to avoid rusting due to bare steel panels ) - high build primer to sand( two part ) - primer sealer to protect outer coat color when applied-no sand - outer coat ( color ) wet sandable - clear coat wet sandable Main rule is use one brand of ingredients. Like PPG from primers to outer coats. If you mix different brand components, paints may not be compatible and will ruin all your work. Good luck Ferd