To spray paint graffiti, you will need the following: 2 cans of spray paint and a mask. You will need to have an idea of the design you want to paint, before you begin this project, because you will need to work quickly. Put on your safety/protective gear. Paint an outline of your design, first, with one can of spray paint. Then, you will want to strategically fill in the design. One can is primarily for filling it in and achieving light and shadow. Therefore, you will need a dark shade and a lighter shade. Continue comparing the project to the sketch until you've reached the desired effect.