I did the sand, buff, polish method on my rear fender to get rid of the gnarled edges from rollovers (i assume on pavement). Its up to you but I regret it. My plastics smoothed out real good but now they don't have that glossy finish anymore. I only did one fender so I could compare and it is smooth but not glossy anymore. I sanded all the way down to 1500 grit then used rubbing compound and then waxed so I'm pretty sure I did the right process but I regret it because my fender will never be as glossy as it use to be.