The glass-bead display can be made to work more easily [than an indoor water spray]. The glass beads used in road markings will work well. I have used "spray adhesive" to attach them to either black cardboard or cloth. The adhesive comes in aerosol spray cans and is available from several manufacturers. I spray the surface in an east-west pattern and then in a north-south pattern to get complete coverage and then sprinkle the glass beads over the surface with a big salt shaker. if you tilt the surface in different directions before the adhesive dries you can roll the loose beads around to make the coverage more uniform.