I am working on an 84 Z28 and have the body pretty well prepped to have paint. I have not done the plastic bumper caps. Can they be sanded like the rest of the car or is there some other precautions I should take?
plastic parts have a system that is a little different. If you are just sanding them for paint and there is nothing wrong with them, then sand them with a medium grit (400 on a d/a or 500-600 wetsand) then seal and paint. If there is damage to them then repair as needed. For cracked paint sand paint down to the plastic. Only way to get rid of crack paint(also known as spider cracks). If plastic is cracked or damaged rough plastic up with a rough grit and use a plastic repair product only. Bondo wont stick to plastic. Before applying anything to plastic however, you will have to clean the plastic with a special plastic cleaner. Regular cleaners do not work on raw plastic. They soak into the plastic and take a long time to evaporate out and you will have problems with paint sticking. Then you have to spray a plastic adhesive promoter to all bare plastic. After that you can primer the plastic parts. One really important part to painting plastic parts is to use a flex additive. Flex additive must be added to your primers, sealer and clearcoats so they can flex with the plastic. Otherwise the paint will crack after it becomes hard and the plastic flexs. If you go to a local paintstore, they should have all the information on how to use the products correctly and which ones you will need to use.