There are actually two reasons for the base coat. This base coat will help protect the nail from the paint and help the paint to adhere to the nail better. Metal should be wet sanded to give a rough grainy effect. This rough grainy effect will help the paint to adhere to the metal. With metal actually being smooth the paint will have a hard time sticking to the smooth surface. The kit contains everything you need to get you started creating airbrush art tattoos and then some. In their starter kit they include 2 single action ABA airbrushes, 2 hoses, 9 glass airbrush bottles, a 2 outlet air manifold, 7 60ml airbrush tattoo ink in red, blue ,white, yellow violet, fuchsia and green and the kit includes a 120ml of black airbrush tattoo ink. Real tattoos are permanent and you are stuck with what ever you get. The only way to remove a tattoo that you do not like is to either do a cover up tattoo or go and have laser surgery to remove the tattoo. With airbrushed tattoos you can get rid of it with baby oil or just wait about 7 days and then it is gone. This feed is great for airbrush art designs that call for fine detail as the gravity feed uses less air pressure. The less air pressure means that you can use slower movements when airbrushing. The bottom feed is where the cup is mounted to the bottom of the airbrush and the paint is brought up via a siphon tube. Imagine being able to create realistic eyes on a dragon you just airbrushed onto the hood of a small model car? When a person looks strongly at your artwork on the hood of the model car they can really see the capacity of the skills that you have as an airbrush artist. Or imagine that no matter what size your project is, even the fine details are brought out to the point that they demand to be noticed. If this should be come damaged then you could have serious problems with your airbrush. Don't worry though it is not hard to replace these parts should there be any damage. Your airbrush will have a handle on which you can hold onto the airbrush with. Airbrush models come with either a solid handle or a handle with an opening.