I agree with Tnstratofam's use of etching primer. You could also use Zinc Chromatic primer, if you care to. Either one will work great for aluminum.
However, depending on the quality of finish you are looking for, will determine the top coat paint to use. If you are merely looking for a covered finish and nothing extremely fancy, Rustoleum will do fine. It can look very nice with the proper application. Not so sure about rattle can finishes though. You get what you pay for.
But if you are looking for a show finish, I would go to the nearest auto paint store and buy some quality top coat paint.
PPG paints makes one step and two step type paints. One step has the base color with top coat already in one setup. You still add a hardener but it doesn't need a clear coat final coat. The two step is a base coat with a hardened clear coat. That type finish can product the most amazing glossy finish you can get. Both types are spray on finishes. Wet sanding and polishing are the ways to achieve those show room finishes.
It really depends on what you want. But the final finish ALWAYS depends on the prep work. That is where you do the most work to get the finish you are looking for. Don't skimp on the prep. The smoothest you can get the primer, the better the final will be. If you can feel any imperfections, they will show up in the final finish...period! JMHO!