Merv

So I purchased some 90mm halo rings and a can of dark teal spray paint to do my headlights this weekend. I've searched around trying to find out on how to prep the surface area once I crack them open,but haven't found anything. The paint I'm using is duplicolor "perfect match". Do I need to just scuff the surface or do I need to really sand it down so the paint can really stick? And should I pick up primer as well? Don't think there is primer mixed in with this paint. Thanks for any replies and I will post up picks of the finished project on this thread.