First, prepare the surfaces of the aluminum. Scuff the surfaces with a Scotchbrite abrasive pad to give a very slightly rough surface for the primer to bond to. Next, clean the panels with a solvent such as MEK or denatured alcohol- this leaves the surface free of greases and oils. Wipe the surfaces with a solution of water and phosphoric acid (Alumi-Prep, etc), rinse and allow them to dry. From this point on, do not handle the clean panels with your bare hands. Buy a cheap spray gun from Harbor freight ($9.99 on sale) and a 2-part epoxy primer from Aircraft Spruce. Spray on the primer and allow it to cure. Finally, a 2-part polyurethane top coat can be sprayed in any color you like. The result will be a hard, glossy, tough finish.
RANDOLPH RANTHANE AIRCRAFT COATING Ranthane Aircraft Coatings. Ranthane requires three separate components (which are separately) that are mixed before application. All three components are required and cannot be substituted: Ranthane polyu
A less expensive zinc chromate primer can be used instead with a good acrylic topcoat but it will not wear nearly as well. An even more expensive approach would be to have the aluminum anodized black.