I think the best resource you have is the internet. Youtube has many videos on how people do their airbrushing. However, you have to remember that no matter what source you use, it is an opinion and not everyone works the same way.
When I started airbrushing, I believed it was an exact science. Since I have realised that it isn't, I have relaxed and got on with it without too many disasters. When I say it is not an exact science, I refer to my experience and my own findings. I use acrylic paint 99% of the time. Depending on the paint,
Tamiya and Xtracrylix i tend to thin, using alcohol based thinners such as Xtracrylix own. I don't use
Tamiya thinners as it is expensive and not always available in the UK. Water can certainly be used with Xtracrylix in much the same way but I personally prefer to use an alcohol based one.
I usually thin at approximately 50/50. I say approximately because I do not measure it at all, I guessed it until I got the results I liked and stuck to the same rough guesswork. I always put thinners into the cup first and then add paint which I then stir up with a cocktail stick until it is mixed thoroughly. By putting thinners in first, it helps to prevent a paint blockage at the first spray as it will be thinners that runs up to the needle. The first test spray to check if the flow is ok will blow any thinners out the way before you spray on the model.
As far as air pressure is concerned, again, I personally do not treat it too seriously. The main reason for this is that my basic compressor, although it has a gauge, it does not really function. As soon as I start spraying the gauge drops to around 20psi and hovers around that point so I guess I spray at 20 psi all the time.
Distance from tip to model varies with how much paint I am throwing at it. If I am going for a small area or fine line, I get in close but don't pull back the trigger too far so I limit the amount of paint coming out. If I am spraying a large area, I spray from about 8 to 10 inches away but pull right back to increase the paint flow. With acrylics in particular, especially using an alcohol thinner, the paint is drying very fast as it gets atomised at the tip. If you get too far back you will get what is almost paint dust sticking to the model giving you a rough finish, get too close with too much paint flow and it will hit the surface hard and wet which results in flooding and spidering, a blob of wet paint with the air blowing out thin spidery legs away from the blob.
If you don't want the hassle of thinning, there is always Valejo
Model Air which is about right for spraying straight from the bottle. I always use it like that although I know some thin it ver slightly, as I said, it is not an exact science. I think the biggest thing you need with airbrushing is confidence. Just have a go with something that isn't important, a plastic milk bottle works well or old CDs and or their cases.
Primer is a good thing. I don't use a special primer, I tend to use whatever grey I have the most of at the time. An even, smooth coat of primer does help in two ways. One, it gives a nice even surface for the finish colour. Bust secondly, and most important to me, is that once primed, you will see much better if the seams and joints are as good as you thought they were. If not, sort them out now and re prime the corrected area until you are satisfied with it. Then you have a blank canvas to start you top coating.
At the end of the day you can read as much as you can and see as many videos as you can find but the set up they use is not the setup that you have. The only way forward is to fire up the compressor and practice.
As an end note, as with all modelling tools, make sure you clean it after use and put it away out of harms way. if you have specific problems then let us know and we may be able to advise on what may be causing it.
