[Zeke]

I don't like urethane, but you didn't mention that one. Anyway, avoid it. It's the toxic one and hard to handle; slow to dry.

Acrylic is hard to beat. Celluose is all but non existant and is not compatible with many undercoats or paints. Synthetic is what I call machinery and maintenance enamel. IOW, cheap. Commonly used by Earl Scheib and the like.

Lastly, polyester is a 2 part, did you say you didn't want to get involved with that? Anyway, it is the best form of primer you can use for build up and block sanding. Didn't know you could get it in auto paint form. Commonly used on boats as a basic coating.