Bear in mind I'm a hobby builder, so this is just what works for me.
If you do a quick (really quick) dip in clean acetone, that will remove the surface layer of the plastic, and make is shiny again. I do that before I paint clear plastic baits. Too slow, and the bait will come apart or melt.
Once I've dipped a bait, I can paint right over the newly exposed plastic with my paint scheme, and it will stick, but not bond. My top coat protects the paint, so it doesn't need to bond to the plastic, just stick long enough to get top coated.
I've got cranks I painted this way that are years old. The finishes are worn, but the paint stayed on them fine. When they get too worn, I just redip them in my top coat, or respray them with it.