Howdy!
I never heard of thinning enamels with lighter fluid. The best method would be using the manufactures thinner.
Nice collection you got there. As far as preferred paints, well that's a long story. Work with what you’re used to for now. Both Testors and Tamiya are excellent paint manufactures. Acrylics have become very popular and I will sometimes use a mix between enamel acrylic and lacquer depending on the effect I'm looking for or what I have in stock at the time.
I would suggest getting an air compressor. It will pay for itself in no time. I found the one I have been using for years on eBay for $20.
Steve