you are painting plastic parts. some of the thinners-solvents are not compatable with certain plastics. the last car I painted was 15 years ago , I got the color free. My son was taking an auto painting class at the college and the fire dept did an inspection of an auto body shop in town and they had way too much materials not stored in fire rated cabinets. The shop had 24 hour correction notice so the owner loaded up his truck and took it to the class and everybody got to pick out what they wanted. Junior picked out 2 colors of the same mfg and type of paint. I went to the auto body-paint supplier in town with the cans and still spent $ 300 for the correct primers for metal, plastic and aluminum trim, reducers. etc. 40 + years ago I spent all summer getting my car ready for paint, I had 2 days before having to go off to college, I rented a compressor and gun. My sister had a brand new house and she let me use her garage. It was over 100 degrees and when I mixed the reducer and tried to spray I blew cobwebs out of the gun. ai panicked and asked a couple guys that I knew and they said wait until it gets below 80 * but no time. so I thinned and thinned and thinned but the acrylic laquer still came out very dry. I went ahead and sprayed it on anyway. It looked like tinted primer, very dry finish. after a couple months to cure I thought i would start to sand it down and recoat. I was using 400 wet paper and the finish looked excellet wet. the surface was smooth as glass . I rubbed out a spot and it looked like clear glass over fine sand . I finished sanding and hand rubbed it out and everyone asked how I got the custom finish.