When you are first learning something new, things can sometimes get a little tricky. You are trying to create a new form of art and are finding that some things may be a little difficult to get to happen. The experts showing you how to do something on a video make it look so easy. You will believe it is easy until you get out there and try to do it yourself. It is at this moment that you realize that you are not able to do what they did. To start with you need to practice with simple techniques until you get the hang of how to do them. Simple techniques will give you a better understanding of the process and allow you to have a foundation on which to build on.
When you first try using an airbrush you need to use a cheap surface that you can just practice with. A simple black paint with work for this. No need to buy additional colors. The only thing you need to be doing is experimenting with the airbrush. Get used to how it works and feels in your hand. Practice spraying the airbrush at your cheap surface while you learn just what pressure is needed where. If you are using a double-action airbrush you should be experimenting to see how far back gives you how much paint spray.
Once you are comfortable using the airbrush then you should work on creating shapes with your airbrush. Using cheap surfaces airbrush circles, triangles, squares, and rectangles. While this may seem stupid it will help you to learn how to create designs using your airbrush. Continue to practice with shapes until you are able to perfectly render airbrushed shapes. Once you have the ability to render the shapes, you can move on to rendering shapes in different textures. This means that you should work on creating shapes with thin lines and shapes with thick lines. This will help you to learn more about how to use the airbrush to render broad designs as well as fine detail.
Now that you can render the shapes you should move on to using stencils. This will give you a feel for stencils as most beginning airbrush artists will use stencils to create their airbrush art. Practice using stencils on a cheap surface and still using your black paint. You will also gain knowledge from trial and error on how to remove stencils without disturbing the paint.
The type of paint that is best for a beginner just learning is Golden Airbrush Colors. These paints are ready to use and will save you from having to deal with thinners and such. Save those types of paints for when you have gained yourself some experience with airbrush art. Stick to ready to use black paint from Golden Airbrush Colors because it really does not matter how the paint looks at this point. The only thing that matters is that you learn the basic techniques so that you have a good solid foundation of skills in which to advance you forward with.