Primer ligth grey cars and caravan

First and foremost, primer helps the paint adhere to bare metal. Without primer as a buffer, the shiny metal surface, whether old or new, won’t bond with the paint well. Equally as important, primer helps prevent rust and moisture damage to your vehicle by adding a couple of extra protective layers.

Apply two thin layers, more if needed, wait 5-10 minutes between each layer. After the last coat, wait 10 minutes and gently sand it with fine sandpaper.