Before you touch a wheel with polish or sandpaper, work out which of the three types you have. Getting it wrong is how people ruin a set of wheels in an afternoon.
Aluminum turns grey and chalky because of a layer of oxide, not damage. Here is how to remove it by hand, which surfaces give the most trouble, and how to stop it coming back.
What makes a non-abrasive jewelers' rouge formula different from the abrasive polishes on the shelf, and why it matters on soft aluminum and thin chrome.