I used to polish the aluminum rims a couple of times a year using a drill, buffing wheels and polishing compounds. The aluminum would tarnish and need some strong abrasive persuasion. Once I powder coated the wheels, it was much easier to keep them clean with regular paint polish/wax cleaners on a monthly basis. On a daily basis I usually wipe the rear rim with a damp micro fiber cloth after every long ride to get rid of brake dust etc. Only takes a minute and keeps the rims looking great.