A suggestion on using stencils. I assume you had trouble with paint bleed under (you mention the glue). A dirty little trick to avoid this is to paint in background color, let dry. Apply stencil, taping in place around outside and make sure it is flat. Now paint again with either clear, or the background color. This may bleed, but it won't matter as the color is the same, and the bleed will seal the stencil. After drying, apply color #2, dry, and remove stencil. For color #3, the precoat strategy will work only if you use either clear as your precoat, or arrange to have the second stencil bordered by only one color, in that case you can use that color as the precoat. When doing multiple colors, much planning is needed to arrange the order, and the overlap, considering the opacity of the different colors (usually the black goes on last, and covers the sins of bleed of the other colors).