I drew it up digitally using a wacom drawing tablet. Then get the image printed on a large format printer... one copy for every color used. Then I sit down for a few days and cut the stencils, one color out of each stencil. Prep that canvas with some newsprint, then spray each layer one at a time. As for lining them up, I create reference points in the corners that don't end up on the finished piece. But in the process of spraying, the points allow for perfect placement.