Priming is dependent on the paint being applied. For example, two-part paints will require an epoxy primer over TotalFair, before applying the paint. Another reason to apply primer over cured TotalFair prior to painting is for the purpose of hiding the color of TotalFair, which is light green. Always check the paint manufacturer's directions to determine whether priming is absolutely necessary.
Though gelcoat is NOT a paint, it's important to note that before applying gelcoat over cured TotalFair, the surface must be primed with an epoxy barrier coat (such as TotalBoat TotalProtect), or an epoxy surfacing primer (such as TotalBoat 2-Part Epoxy Primer).
DO NOT apply gelcoat directly on cured TotalFair, or the gelcoat will not adhere properly.