Wipe with a spirit based cleaner. The best is methylated spirit. It is also a good move to wipe the surface in a very thin, wish washy methlated spirit. Some that you've previously used to clean your sunkorite impregnated paint brishes is a good bet. The best surface to adhere to is light bead blasting, phosphate and paint but if you haven't got phosphate facilities, then bead blast, wipe clean with the paint brush cleaner meths which acts as its own primer. Bake, then spray then bake again