Sand it with a piece of wire wool thats all ye need, jist tae givew it something to cling to....but a`ll tell ye Matt Black is not a good colour to keep clean, ye see finger marks on it an stuff, its very gard tae keep it good...if yer painting it why not paint it a different colour....whit about Blue, as I have a tail piece, front headlight surround, an two scoops all fur a reasonable price....pm me if yer interested....John