I absolutely swear by Iron-X - looks to be similar to the post above where it turns red when washing. You use a spray-bottle to apply and simply rinse off. I've used this on wheels I thought were way beyond being able to clean properly and this stuff is magic! No brushes, no scrubbing - simple towel dry at the end and your wheels, calipers and even most of the inside portion of the rim are spotless!
Iron X Iron Remover, CQuartz IronX, Paint Cleaner, paint decontamination
I agree with 3s-a-charm, ironX is an incredible product, however it's on the pricy side.. I paid 120dollars cnd for a gallon.
there is another product that I believe works as well as ironX,(so far my favorite as well) is wheel brightened from maguiars. I am trying to buy some however Amazon.ca does offer the product in Canada. If you go on eBay you can find it at a slight discount compared to iron. I am suggesting this alternative product from recommendation from Darryl at autocarfetish.