All good advice, although I prefer to mix/thin the paint in a separate container, as it allows more positive control, the shade and consistency of the paint can be gauged, and it prevents the mottled shirt effect!"
I use a plastic shot glass, or one of those small plastic tubs used for medicines to mix the paint in, then transfer it to the airbrush. A mix might start 50/50, but can sometimes go to something like 60% thinner or more, depending on the paint and requirements. Basically, when it runs down the jar/glass/mixing container like milk, then it's in the right area of mix ratios.
If you have an airbrush, use it - don't sit looking at it,being nervous. That's like owning a car and being afraid to drive it.Practice mixing various paints, and practice spraying various patterns, lines, thin lines, large areas, whatever, onto anything to hand (the wife's hair tends to get a violent reaction). Once you think you've got the 'feel' for the brush, have a go at doing a basic colour on a 'scrap' model (I keep an old and battered 1/32nd scale P-51, just for experimenting on), then, bite the bullet, and try it 'live' on an actual model.
As for 'rattle cans' - if you have a wall which needs graffiti, fine - if not, then throw the things away.