i didnt use primer, nor did i use clear coat and mine is still in great condition after months over 10 months of Arizona sunshine beating down if i wash it off with a washcloth to remove the dust looks just the same as the first day i did it, i used duplicolor interior paints, i would suggest first cleaning off the panels u are painting with at least a wet cloth to prevent getting dust from getting under the paint which would promote cracking but most plastic interiors are not smooth so a primer is not needed, a clear coat will prevent the paint from fading over time, and will give it a glossier glassier appearance, i found i didnt need it but if u want ur interior paint glossy more power to u, good luck guys