Get it hot and wipe with a COTTON cloth. VERY light rubbing with a metal scouring pad maybe too. Get's most off (go on..ask me how I know ) and then Autosol.
I just would take the metal brush and work it off. Afterwards with a metal sponge... After a ride the natural color of the blank metal will come back as ig did getting it from the dealer the first time. I wouldnd take any agressive chemical to be honest... Maybe also some fine sand paper... Done.
