Use rubber gloves...
I have some tips. First try SUDSY Ammonia. That is SUDSY Ammonia not just plain Ammonia. You may have this already if not it is pretty cheap at the store. When using this, always have clean water available to wash the surface to stop the action of the ammonia. Use in a well ventilated area like outside in the garage or just plain outside. Use a cloth and try it on a small part of the black first to see how it does with the black paint.
OK, if this does nothing the next to try is any brand of liquid sandpaper that you may have on hand. Liquid sandpaper is what you wipe on painted surfaces to 'cut' the surface to prepare it for painting. It goes by different names such as , Surface Conditioner, Preparite, Liquid Sandpaper, and others. Different brand names have different chemical compositions and work faster or slower. Use this liquid on a cloth and rub on the black paint. Black showing on the cloth shows the paint is being removed. Always have clean water available to flood the surface to stop the action of this chemical also. You only want the black overpaint to be removed and nothing else so if something else is coming off, quickly flush water on the surface to stop any chemical action.
