auto painters---topcoat choices

[MS Fowler]

OK, I've stripped off the old paint, treated the clean metal with a phosphoric acid material to remove the microscopic rust and prevent future rust and improve bonding of the primer to the metal.
After priming and sanding all the panels to flat I will be ready to topcoat.
Due to financial constraints, i will be using Kirker products. My choices are:
1) Base Coat/Clear coat-using an acrylic enamel that has been modified with a " base coat stabilizer" that allows recoating in just a few minutes. This stuff is a lot like spraying old-fashioned lacquer--it dires that fast. Top coat will be a clear urethane enamel.

2) Single stage urethane enamel.

Everything I read gives the advantage to the Urethane enamels, in terms of gloss, srayability, and durability. I wonder how well the BC/CC will hold up. Will the color coat, being an acrylic enamel, hold up as well as the urethane enamel would? Will the fact that the CC is Urethane increase the durability of the underlying enamel ?

Another question; The directions for both the Urethane Enamel, as well as the BB/CC advise adding some clear to the final color coat. How much is " some"? Should that final color coat be half color and half clear? or some other ratio?

Thanks for your help.