I've used chore boy copper scrubbers and 0000 steel wool, both with WD-40 to lubricate as you scrub, both work, but both leave fine scratches. Oh chrome though a good paint stripper should do the job and won't mess up the chrome. Last night we used an angle grinder with a twisted steel brush on it to remove silver spray paint off of a chrome chainring, it removed it with no noticable scratching and no removed chrome, and this was a newish cheap-o chainring. Chrome is forgiving, scrub away.