Beginners should invest in either a bottom or siphon feed airbrush. Stick with a brand name as quality tools and parts are fairly easy to come by and it’s much easier to find help when issues arise. Regarding paint, any good water-based illustration type airbrush ready paint will do.
Step by Step guide to Airbrushing
1) Hold your airbrush as you would a pen with your index finger on top of the trigger. You can drape the air hose over your forearm to keep it out of your way. Both your hand and upper body should be relaxed. For now, hold the airbrush perpendicular to your painting surface.
2) With a double action airbrush pushing down on the trigger gives you air, pulling back gives you paint and doing both gives you air and paint. Practice pushing down the trigger; get in the habit now of always leaving the air on while airbrushing. Try pulling the trigger back to release paint as well as air. With a double action airbrush, the further you pull the trigger, the more paint you will apply.
3) Practice moving the airbrush towards and away from the paper. The further you are from the surface, the paint will cover a larger area as well as being less defined. The opposite is true when you move closer.
Drawing a line
Using both hands to steady you, turn the air on, and slowly move the airbrush across the paper keeping your wrist locked. Pull back on trigger for paint and follow through with just the air on as you come off the paper.
The closer you are to the paper the smaller and thinner the line will be. The further away from the paper you are the larger the line will be. Do several lines, trying to keep them as straight as possible, all the way across the page.
With the airbrush at right angles to the paper, pull back on trigger to make a dot, and move across the paper making dots.
Practice doing a page of dots and then joining them together with lines.
Hold the tip of your airbrush several inches back from the left hand side of the paper. Start moving your airbrush right across the page and lightly apply color as you go. With the air still on, go back to the left side of the page and start all over again. Your goal is to cover the entire page in a nice, even shade/tone with no signs of starting or stopping.
The dagger stroke
The dagger or rat tail stroke is very useful. Often used in lettering, it goes from being wide doing to a very thin point. Begin with the airbrush slightly further away from the paper and as you sweep down, move the nozzle closer. Practice making daggers in all different directions until it becomes second nature.
This is another good exercise for helping gain control over the airbrush. Spray loops all the way across the paper, trying to keep them all exactly the same height and width. Once you can do this, try making loops with one side fat and the other side thin.