If you don't have a self-adhesive lampshade, create a pattern by wrapping a large piece of kraft paper around your chosen lampshade; mark with a pencil. Cut out the shape and test-fit the shade pattern over the existing shade. Make adjustments where necessary.
Use the kraft paper pattern or the pattern included with the self-adhesive lampshade to cut a shape from watercolor paper.
Spray the back of the stencil lightly with stencil adhesive spray. Position the stencil on the center of the watercolor-paper cutout. With the spreader, apply white Texture Magic dimensional paint over the stencil area. Remove the stencil and place it on a piece of waxed paper. Scrape excess paint off the stencil and place it in a plastic bag. (Texture Magic is reusable.)
Clean the stencil. On the watercolor-paper cutout, place the stencil over the last row of diamonds on one side to line up the pattern. Spread with Texture Magic, remove the stencil, and scrape off excess paint.
Repeat step 4 as many times as needed to cover the entire shade. Let the dimensional paint dry overnight.
For a wash effect, thin Putty paint with water and brush the mixture over the stenciled watercolor paper; let dry. Wrap the watercolor paper around the lampshade, and secure it with glue. (Note: Once the dimensional paint is cured, you can place rubber bands over the paper to help it shape to the lampshade.)