My C5 body has many gouges, grooves and deep scratches in the shell from poor abuse in the past. The below steps are what I have done to improve on the condition. *Note: That the results are not perfection, but an acceptable quality that I am happy with.
1. Take a razor and remove any curled over material in the plastic to level out the section.
2. Clean any plastic part well with detergent that will not leave a film behind.
3. Apply a skim coat of glazing putty to affected area and let stand to dry.
4. Sand glazing putty down to surface until smooth. Repeat Step 3/4 until satisfied.
5. I have painted the parts with Krylon Fusion paint for plastics with good results. Not an identical factory match, but a good look and satin finish. The color I used is 2439 Satin Pewter Gray
Below are photos of products I used, Wheel covers during glazing steps and wing mirrors after finishing and painting.
You can see above where the putty has filled in the deep cuts in the plastic after I have sanded the cover smooth.
This is a photo of the finished wing mirrors after I have done all steps above. Mirros are painted with the fusion paint.
This is the glazing putty and fusion paint I have been using on the body surfaces.
Regards,
Adam