Eugene!
I used to build them years ago. When I owned my Auto Collision and Repair Shop. What I would do is put the bodies together and then use Fibreglas repair kits on the center seam. I would then sand till smooth Prime with "Ditzler-Finish Prime" and then when I had to paint a car I painted them with the same paint.
But, Black or Metallic Brown for the Fenders and such.They were fun and I discovered if I fastened the wheel halves together with epoxy, I could then do one wire at a time with stainless wire till the plastic ones were gone. I had them in a case in the office. It got me some Resto-Business locally(Good Money that!).
I also had a Packard that I bought as a Barn Collapse Find. Restored her and got the engine to run after the time in the barn from 1938 till 1980. Did a total rebuild cause at the time I had parts contacts (Red Line) and It and the Hubley model were exactly the same! So they would go to shows together. By the way, none of my restos were Trailer Queens. I drove the longest from Little Rock to Pebble Beach for the Concourse De' Elegance In the Packard! The Missus would follow in the R.V! She loved that Big G.M.C. Diesel Pick-um-up! So where I went so did the fifth wheel.