How To Prevent Paint From Seeping Under Your Stencil . a thin layer of matte medium around the edge of the stencil. This prevents the paint from leaking under the stencil and creating a big mess for you .
Art Teacher Hack: Line brick/cinder block walls with two rows of masking tape, and use hot glue to attach top corners of mounted art to the wall. Stays up as long as you need it to, and pops off easy when it's time to take it down.