the best solution is to soda blast the vechicle it removes the paint but damages nothing in the process. it is messy though . if you were to use a stripper as suggested by another use an aircraft stripper as it will not damage the aluminum as the regular chemical base strippers are caustic and causes degradation . after solvent clean and scuff using a cross hatch sanding method

Whatever you do, do NOT sandblast. It is too rough on aluminum. You can use almost any good grade of paint remover, but just as a precaution, I would suggest trying it on a piece of scrap aluminum before using it on the body of your car to make sure it does not harm the aluminum. As for the primer, I recommend us of an oil base, or enamel base primer in preference to the usual primer surface. It is slower, but better and will last longer. You might possibly consider paint remover and primer from an aircraft supply house of the type used on commercial aircraft – which are constructed out of aluminum. As for repainting, I would recommend lacquer and apply several coats, and water sanding lightly with 400 to 600 grit wet or dry emory paper between coats to build up depth and beauty.