Are there special products like undercoat for plastic vs metal gas tank and do I have to sand decals off plastic vs metal?

 

My wifes F3 fell over in a parking lot and needed to be repainted. I peeled the decals off, however it left a lot of glue residue on the paint. I used Lacquer thinner on it to remove the glue. I know what you're thinking, but the paint is not a lacquer based paint so it doesn't melt. I kept the lacquer from getting on the bare plastic areas so it wasn't an issue with the plastic either. Naturally I did it quickly to minimize the risk, but it worked well. I didn't have any metal places (ie the tank) to do. I suspect since the clearcoat is over that you'd need to sand. Hope this helps.