i got a plastic reviver thing for my corona, white spray bottle, good shit, brings them up nice up black for a couple of weeks just need to be careful how you apply it don't get it on the paint it stains. Just get an old singlet/rag clean of course, spray a little on it and run into the bumpers, that or you could use tyre black, we spryaed the bumper on our pajero with it and the side stripes before we took it in for evaaluation for a trade in on the camry and hey looked pretty good.