I've been using a Paasche VL for the past 30 years or so. It's easy to clean and parts are readily available, should you need them.
Whichever airbrush you end-up with, the most important thing to remember is to keep it clean, and that means cleaning it thoroughly immediately after you've finished painting.
When you do finally get your airbrush, pick up some corrugated cardboard boxes from a local store, and, after flattening them or cutting them up, use the blank side to practise on. This will give you a good opportunity to try different brands of paint (they have different characteristics for spraying), and also allow you to see the effects of varying the paint-to-thinner ratios, and that of various air pressure settings. Likewise, varying the distance between the airbrush and the work will give you different results, and this is an inexpensive way to learn what works and what doesn't.
The instruction booklet that came with my VL outlined a few simple exercises to practise in order to become comfortable with the tool, and one of the best, in my opinion, was the dot and line technique. You can use a pencil to draw a grid on a piece of cardboard, or do it totally freehand. The first step is to make a series of dots at the intersections of the grid lines: this will demonstrate the correlations between paint/thinner ratios, spraying distance, and paint/air ratios. The object of this part of the exercise is to get the smallest, cleanest-looking (with the least spatter) dots that you can. When you've mastered that, practise connecting the dots with the straightest, finest lines that you can make. While you may never need to apply dots or lines to a piece of rolling stock, these simple exercises will teach you the capabilities of the tool and how to control them to your best advantage.
Wayne
to start working on it.