mrtexas, I admire your personal effort to do all the work yourself on a budget with what you have at hand (no paint booth). This is how I operate also.
Marvin may have a point that there are better ingredients in the more expensive stuff, however IMO, it depends on how the vehicle is going to be used. Maybe the expensive stuff will hold up to the sun's UV rays without chalking better than the cheap stuff, or may resist chipping by rocks better, etc. But with an old Model A that sits in the garage most of it's life and may only be out all day in the sun for an equivalent of 2 or 3 straight weeks per year, and sees proportionally less rocks tossed at it than an everyday driver, I think some of the cheaper products are just fine, and will probably outlast you if you look after it.
A friend of mine who is gone now, used to paint with a house brand cheap industrial enamel from the local Cloverdale paint store, and because of his years of experience he could lay that stuff down just like glass and almost never needed any buffing or polishing. You would swear it was some kind of expensive paint, and he would just smile and tell you, no "it's the cheapest stuff I could find" Now many of these vehicles he painted were for their own collection and would sit on display in a building and hardly ever see the road or daylight, but after 5-20 years, they all still look great. He proved to me that a decent job could be done with the cheap stuff if you know what you're doing.