Southern Polyurethanes SPI 2K High Build Primer is great for smoothing car surfaces before painting. It will fill in imperfections on the metal finishing. It will help the paint stick to the car as well as resisiting moisture damage caused by water permeation. This high build primer comes in gray gallons only and has a 4:1 mix ratio with the part# 7001-4 activator, which is included with purchase.