My biplane originally had auto paint over dope. Lots of cracks before I recovered it. Although latex is not for me, it maybe right for another.
My Fisher had auto enamel over Ceconite 7600, which was a forerunner of the Stewart system. Lots of cracks. When I had to make repairs, I used the Stewart repair technique, which can be used over any system, and topcoated with the original enamel.
House paint is probably OK too, there's a Minimax sharing my hangar done that way. Looks good but heavy, I think he used too many coats. I don't think it's the right thing to use if you plan to topcoat it with anything else, though.
What’s “Ranthane” from Randolph?
Is that a top coat that’s used on the Polyfiber system?
No, that's the urethane topcoat for Ceconite, over dope. Randolph was the dope supplier, but now it's under the same roof (Consolidated Aircraft Coatings) as Poly-Fiber. The Poly-Fiber urethane is Aerothane. For all I know it's the same stuff, but you have to stick to one process for certified stuff so they have both.
The Randolph dopes used with Ceconite don't smell bad to me, maybe because I grew up painting model airplanes with dope. Toluene is the solvent. The smell of the Poly-Fiber chemicals (MEK solvent) just scream, "TOXIC!!!" to me, though I don't know if it's any more harmful than toluene. But Poly-Fiber is easier, if only because it takes a lot fewer coats than dope.
If I was covering a plane now, Oratex would be my choice because I hate painting. Otherwise, I'd go with Stewart.