FYI American wheel has a polish in a can that kind of reminds me of NEVER Dull, however it is by no means the same product. I have used this for the past 2 years and it works very well. The spots could be stains, with that in mind I think I would use the manufacturer's suggested product to try and remove unwanted stains and marks. The secret to polishing alum wheels is easy on the pressure, so as not to add scratches to the mirror finish. Another good product for these wheels is Eagle One, get the PH balanced . Water will also spot alum. The method for cleaning your wheels should go like this. Cold wheels, first wash them with the Eagle One product and then polish the rims. Apply the polish and let it haze before buffing ( hand buffing )
Hope this gives you some insight .