I used to polish aluminum parts for historic engine parts on Porsches, we used jewelers rouge and a grinder with a wheel/cloth attatchment. Different wheels for different sized parts, this stuff had to be perfect, most of the cars were rarely driven, all trailered to concours shows around the country. I doubt any window cleaners polish aluminum frames....BUT, you never know. It's tedius, time consuming and without the right equipment the results will show with some shiny spots and dull spots. The stuff we did, looked like chrome when done. Corrosion and pitting will make it all that much tougher with the height difference on the surface. If it were me, this would be something that I would possibly try a frame for the customer to see if they liked the desired end result, and or, have a professional polisher bid the job for you, he's going to have all the small type of cloth polishers and compounds to make them shine, he bids it, add in your percentage. Let him do the work, it's what HE does and what you do is stick to cleaning glass, your profession. In the end, the customer is happy because you took care of it, did the leg work, got the job professionaly done, everyone gets paid, everyone is happy.