Interlux Pre-Kote Plus Primer and Undercoat. Offering substrate protection and an ultra-smooth surface all in one. For use above the waterline with Interlux one-pack finishes and deck paints, Pre-Kote Plus can be applied directly to most substrates, including properly prepared metal. It has lower VOCs, is easier to apply, and has improved flow and aesthetics compared to primers or undercoats alone, making painting easier for DIY customers while providing the perfect foundation for your topcoat.