Personally, I wouldn't use automotive products. I know plenty of people on here do, so I know there are some that work, but I have attempted it 6 times with different 2k automotive paints, and each time resulted in failure. I don't do it any more. You could have more luck with 2k marine products, but they are more expensive and then you might as well go with Duratec anyway. Duratec is made for the job and will work every time. Otherwise, PVA is guaranteed success, it just requires a little bit of post-finishing work. 

One things for sure the uni system hates rattle can paint, i know i spent 2 hours scraping the paint off the mould! D'oh! 

Problem with epoxy tools is they aren't UV stable, and they don't polish to the same high level of gloss that the ester-based tooling systems can. They also are unlikely to take as much heat as a vinyl tool. 

For that reason, unless I have sprayed a plug with the surfacing system that I know is compatible with my gelcoat, I only use PVA on plugs. Forget the wax, just spray 4-5 coats of PVA onto the plug and you won't have compatability or release issues.