I’ve seen the experts using a sticky back paper to mask off areas and using a sharp blade to cut around what they want to leave. Presumably, the next coat or coats of paint is going to fill in the minute score line from the blade. Having a paper backed mask over your base/clear to shoot your single stage might be doable. I’m no hotshot painter either, but your tailgate is a relatively small area, and if it turns out like less than you want it to, isn’t going to take a lot of work to re-do.
