I found a great way to deep-clean stained wheels.
I'm about to polish and seal my car. But first, last weekend I wanted to clay it clean. I figured clay is clay, so I got the turtle wax ICE wax clay bar kit because it was cheapest and the bar was 20 grams bigger. It comes with their "liquid clay bar", which you're supposed to use before the clay. It sounded like a gimmick and I wasn't interested, but I figured since I had it I might as well use it. I could take it or leave it on the body, but this stuff works wonders on the wheels! It got all the grimey stains from baked in brake dust off no problem. I followed by clay, but it didn't really make too much difference except for a few tar stains. Not sure if it'll work on the caked & baked brake dust inside the wheels. Anyway, it was very effective and very easy to use.
I just got the porter cable polisher, so I'll follow up tomorrow with polishing and Klass AIO & HGSG, as has been recommmended here