No real limitations but I'm interested in the proven methodology and materials. To "sand it and spray some etching primer" seems vague given the known difficulties of long term adhesion to aluminum substrates. I expect an abrasive blasting to be in order but with what media? Is glass bead aggressive enough? Is a wash of some sort required after blasting? When this oxidation occurs around a penetration, for example body molding clip holes; how is the interior of the skin (inside the door) best addressed? Is there a particular filler (for the local pitting) that will support the encapsulation?