to the forums! Pull up a keyboard and stay a while.
I'm assuming by the scale that you are a railroader, of which I'm not too familiar. Floquil RR Enamel is a very nice paint, and it is slanted towards the trains. Polly Scale Acrylic is also a good paint and also has a railroad line,
Airbrushes are a personal matter, and you will likely get a bewildering array of answers.
My favorite brush is the trusty Badger 150 dual action, siphon fed with medium and fine head/needles for the 1:48 modeling I do. It would serve you very well, and if you want finer lines the Badger 100LG is a dual action, gravity fed airbrush which shares parts with the 150. It would require more refills of paint compared to the siphon fed, though the color cup is quite large compared to the 100G (which is my next airbrush, don't tell the wife! Shhh).
I do note that fine heads have a greater tendency to clog than medium heads, and the difference in line width is not that great. I use only Tamiya Acrylics for my WWII warbirds, and I thin them quite a bit with the fine head/needle combo. I know next to nothing about enamel paints, but assume that they have larger particles which could be a pain.
Good luck and Happy Hunting!