Removing the needle cap is fine but should you hit your airbrush against something or drop it you could end up damaging the needle itself. So to take care of your airbrush make sure that when you are not using your airbrush that you replace the needle cap back onto it. This will give a little protection to the needle itself should the airbrush happen to fall. If you are doing a mural on a wood floor then use a hand floor sander. You don't want to mar the wood only remove any rough areas. If the wood has been waxed or has a gloss coat then sanding this will remove this and allow for the paint to stick to the surface. Skin should be cleaned with rubbing alcohol to remove any oils from the skin. Those that apply make up are considered artists and airbrushing on makeup is just another great way that they have found to show off their artistic median. The make up goes on water and has to dry. As it dries those watching can see the transformation of the subject from what she was to what she is now becoming. While the book will teach you some intricate designs do not worry though cause the book, also has some simple projects that you can start with when working with airbrushing motorcycles and cars. If you are at an intermediate level with airbrush art then The Ultimate Airbrush Handbook by Pamela Shanteau is for you. With single action only the air is controlled with the trigger. The trigger will control the air and the amount of paint that comes out is determined by the needle adjustment on the back of the airbrush handle. Dual action is when the trigger on the airbrush controls both the air and paint. The trigger is pressed down for the air and back for the paint. Always keep the iron moving though so that you do not burn the material. Another great way if you are doing this at home is to allow the design to dry then turn the shirt inside out and throw it into the dryer for about 40 to 45 minutes on the highest heat setting. After this your design will hold up to laundering.