To prepare your pre-finished steel garage door for painting, it is important to give it a good cleaning, but do not wax.
Remove surface wax to prevent the paint from peeling or flaking. Lightly scuff the surface with a fine steel wool pad saturated with soapy water. A final wipe and rinse should be done with clean water only to remove any loose particles and any soapy film residue. Remove surface scratches which have not exposed the metal substrate by lightly buffing or sanding with 0000 steel wool or No. 400 sand paper to create a smoother surface for painting. Do not over buff or sand the garage door, because paint will not adhere to the door if the surface is too smooth. Do not attempt to remove scratches if your steel door surface has a finish painted texture representing wood grain, stucco, etc. because of the increased danger of exposing the metal substrate. Simply paint them with a high quality metal primer. Follow drying time on primer can label before applying topcoat. To prevent rust from forming, treat any scratches that have exposed the substrate by sanding the exposed area lightly and then painting with a high quality metal primer specifically intended for galvanized surfaces to protect the area from corrosion. Follow drying time on primer can label before applying topcoat. After properly preparing the surface according to the above instructions and allowing it to dry thoroughly, coat the door with a premium quality latex house paint. Follow the paint label directions explicitly. Oil base paint is not recommended. Note that if substrate is exposed, painting with latex paint may cause accelerated rusting of steel. Follow previous instructions on priming the door for painting. Re-painting of a finish painted steel voids any pre-finished surface warranty.