Auto body repair & detailing: rear bumper cover, mustang gt, sand paper

Question
I have an 87 Mustang GT & I want to get it painted, but need to do some repairs first. The rear bumper cover (which is plastic, I guess) is not smooth. It's got like knicks or something in it. What do I need to do to fix it? Any help is greatly appreciated.
Thank You, Terri

Answer
Terri,  

First sand down any high spots and ridges with 180 or 220 grit sand paper with block or DA sander.  Then take small pieces of the sand paper and scratch up the low sub level spots. Dust and clean with alcohol, then apply Evercoat Polyester, then sand to flat level surface with block or DA sander with same grit sand paper, then finish with 320 then 600 grit and scratch pad the rest. you are then ready for primer or basecoat after dusting and wipe down.

Thank you,  

Mike and Lisa