I am not recommending this, because results that make me happy might just piss off somebody else - but years ago, I bought a used CAV15 MKII polymer AR15 lower. A previous owner had tried to remove the safety/selector (which can be difficult in some cases), got frustrated, and tried prying it out with a screwdriver or something similar. End result, he marred the lower near the selector.
IIRC, I leveled out the gouges with sandpaper and then rubbed down the entire lower with 0000 steel wool to make the entire finish match. That worked because the manufacturer used colored polymer (rather than spray painted plastic). The CAV15 didn't have any fake checkering; if it did, I would have masked it off with duct tape, like I did the serial number and other identifying info. I was happy with the result, but obviously YMMV!
As always FWIW, IMHO, etc.