Althought my bike is not black (Red C10), I've used Mother's Plastic Polish to rub out some serious scratching on a front fender, that had some depth to them. Scratches were caused when a manual garage door coming down on the fender.
I tried it as I had nothing to lose and to my surprise it worked very well. You can't tell the scratches were ever there. Also use it on the windshield as needed.
I've used it sucessfully to remove scratches on painted plastic, clear plastic and painted metal (fuel tank).
