Make sure that your compressor is rated for the type of work you are going to be doing. In this case it will be airbrushing t-shirts. When doing airbrush art onto t-shirts as a business then invest in a commercial air compressor. It will be worth it in the long run. Most of the times you will need to heat set your paints so that they can be washed without fading or bleeding. This will create a atomized fine dot spray pattern. This makes the internal mix a good choice for fine detailed work in your airbrush art. The point at which they come together is in the head assembly. The external mix is where the air and paint come together outside of the head assembly or the fluid assembly. Working with an expert can also mean signing up for some private one on one lessons that will give you more direct attention from the instructor. This could give you a little bit more of an edge over taking a work shop where the instructor has many people to teach at one time. Once you have mastered your skills in micro airbrush art you will be amazed at the amount of detail that you can place in any airbrushing project. While under the supervision of an expert you can quickly learn where you are making some mistakes with your work. Expert instructors include Peter West and Pamela Shanteau who hold classes at the Learning and Product Expo: Art for beginners through to advanced. AirBrush Action offers their Airbrush Getaway Workshops that run from a one day class to four day classes and are located in Las Vegas, Nevada. You can heat set by placing a protect cloth between the design and the iron and ironing the design or you can turn the material inside out and place in the dryer on high heat. If the acrylic does not require heat setting on fabrics then you should still protect the design from fading when washed. To do this place the clothing into a sink of cold water and salt and allow to soak. A damages needle can be disastrous to your ability to create high quality art, because if you are unable to straighten a bent needle back out or the needle should break completely you will not be able to finish your airbrush art until you can get a replacement. If you do end up bending your needle you can try and straighten it with either pliers.