As all G8X owners know, the brake pads/rotors generate more dust than a freakin' lumber mill, even under light usage.
A quick tangent: when I first got my car, I couldn't even figure out how to get my wheels legitimately clean. In the end, that turned out to be easy–just get a bottle or 10 (they go quickly) of
Magic Wheel Cleaner or
Adam's. These contain a special chemical that bonds to iron in the brake dust, and you'll see it turn reddish-purple as it chemically reacts with the brake dust and does the work for you. Let it sit for <= 5 minutes, then hit it with the pressure washer + foam cannon. You should not need to do anything else except dry them (I use a DeWalt cordless leaf blower to dry my car, including the wheels).
OK, back to the real reason I decided to post this: Some time ago, I began to get very irritated that I kept exerting a lot of energy to clean my wheels, only to have them already turning a reddish-brown color within a couple drives to the store and back. I turned to my professional detailer. She hand cleaned, polished, and ceramic coated my wheels (with
this product). It took her around 5 hours, and she charged me $300, but I can tell you it's the best money I've spent on my G82 to date. Now I can drive 10 times as far before brake dust starts accumulating on the wheels to the point that it pisses me off. I still use the magic wheel cleaner so I don't ever have to touch my wheels with anything that can scratch them.
Anyway, that is all. Get your wheels polished & ceramic coated, and then thank me later.