I have small molded plastic mudflaps on the rear of every wheelwell. On the front ones, the paint is cracking and flaking off where the plastic meets the paint. I've removed the mudflap and painted with touch-up paint. This works for awhile, but not it begins to crack after a short time. What can I do to really paint this good? I don't think the touch-up paint is the stuff for the job. Do they make spraypaint in the same color as my car? Also, I have basically the same problem around the plastic thing that surrounds the gas cap. Any suggestions on this? TIA.