Painting ???

Rattle can is rattle can. If you can find the color you want in say krylon or rustoleum enamel, your are getting the same product.
The appeal for them mixing it up is to match a color that the rattle can industry does not provide.
If you just want say... argent or black, buy the rattle can in Kyrlon or whoever.

1K paint is junk no matter what you pay for it. Here is some good info http://www.eastwood.com/1k-coating-vs-2k-coatings

X 2! if you will be playing with these old cars for years, IF NOTHING else , get a 20 gal used compressor and a $50 HVLP gun and buy real primer and paint, the PPG or DuPont or who evers second line of primers and paints. find a real auto paint store. you will light years ahead.