Hey guys - my 3 is lowered and like many, have scratched up the plastic “under skirt” that snaps into the body of the car. I’ve scraped it up enough to where I’d like to smooth the plastic area just in front of the rear wheels (that little flap). I’m not the handiest guy in the world so I’m not as experienced with sandpaper. I didn’t know if anyone else has done this or can simply provide some advice on what grit to mess with? I didn’t want to go to low and scuff it up too much, but I know it is thick and durable.