In this section of Airbrushing 101 were going to be looking at the last main part of the equipment the paint.
This is really a gigantic subject and in no way will I be covering all of it. I will be looking at airbrush specific paints and hobby paints and what you need to do to to make them work with an airbrush. There will be less comparison and this section is slightly different to those that precede it as I am no expert on paint.
Airbrush Paint - This includes Createx, Testors, One-Shot, and even Vallejo Air paints which are all made and formulated to be put through a airbrush. Each brand has different lines intended for different things such as painting cakes, nails, automotive, and t-shirts. They are all formulated for specific applications and while not necessarily for minis most of them will work. The nice thing about these paints is they will either come ready to be pushed through a airbrush or the brand will have some form of thinner they sell that is formulated to go through as a 1:1 or 2:1 ratios. Thus you only need to mix two things with no special formula thus it is quite easy for use. The one fault that these have is they are generally softer than hobby paints (although I would assume Vallejo Air wouldn't have this problem) thus don't take as much wear and tear and will rub or even possibly peel off if they are handled too much however a nice varnish or clear-coat should eliminate that problem.
Hobby Paints - These are the ones that we are all used to painting with on a daily bases and are intended to be applied via a brush. They have far more pigment and generally the pigment particles are larger and coarser than in Airbrush ready paints. Thus even with a paint being thinned well you may run in to problems with clogging more often. This is going to be where you have to work some magic with a nice mix of paint and other additives to get it through the airbrush with as little clogging as possible. People add lots of different things to thin down the paint water, windex, and flow-aid are just some of the things I have seen or heard of people adding to the paint to thin it and make it easy to push through the airbrush.
Ink/Washes - Not really "paint" but ink and washes are great for quick shading. Its almost the same as when you do it by hand but at the same time quite different. If you use ink and washes already then you should know how to use them. Nice thing for them is you can dilute them with something like matte medium or even water to get them down lighter than they were and possibly add other properties as well. Shading can also be done in other methods such as "pre-shading" but those are techniques that could possibly covered later.
While the above is mostly general information I do hope its somewhat informative. Possibly later on I can discuss more specifics such as how I mix my paint and how others do it as well. Maybe even some techniques that can be used to achieve better results.