I've just got wheel arch extensions which are black plastic and run from my front/rear bumber to my side skirts. My side skirts and bumpers are both the same plastic and colour (not painted) but my arches are really smooth and because they are so smooth, they look like they are painted black. Does anyone have any tips on how to make them look like the bumpers e.g. get them a bit rougher? And no, I dont want to colour code the bumpers etc. Thanks.