Had a chance to apply Iron-X Gel (that keeps it where you want it) over painted Opti-Coated wheels. I prepped them (was breaking in a new set of rotors and had more "break dust" than usual) by washing with car wash soap and water. After washing they looked very good, but while drying, I noticed a couple of crevices were still dull and discolored. Applied the Iron-X Gel by hand, rubbing in with rubber gloves (Iron-X stinks, so this is the worst part of the application process). Let dwell for 6 minutes (was a little cooler day). I could not believe how much purple staining appeared on (what I thought) was a clean wheel. Rinsed off to reveal a super shiny clean wheel. Gave it a squirt of 10% Permanon solution and called it a day. That was two weeks ago and they still POP.