I've used.
 

I might as well throw my penny in. Or dollar .. or is it cents.. :confused: :o
Oh well.. here goes..

I used a brand of Graffiti remover. It was environment friendly. The types they might use at high schools. So no this isnt' a license to go and rob your high school buildings manager/caretaker :p
You can get it online somewhere either in a small tub or spray.. it works really well on most paints and i think being plastic based its not likely to destroy the heck out of your joes..
The only thing i'd advise is make sure your either outdoors or have well ventilated areas when using it. :)
Rich