Hi Hank

With any paint job preparation is the key. I would take it back to bare Plastic, this way there is nothing to fail later and wreck your paint work. There are plastic primers around, but it is best to use a paint system from one company, this would include primer, sealer, base coat, clear coat, reducers etc. By using the one paint system you are assured that the various products are compatible, which is important for adhesion, longevity and final finish.

Hope this helps
Justin