just got started, but with plexi at 90 bucks for a largish sheet, I went with the 8 dollar clear shower curtain, stretched onto a frame like a muslin flat, insert painted fanfold 1/4 inch styrofoam insulation as the stencil behind it. Dull down the front of the curtain with a little spray chalkboard paint. I"m really pleased with myself so far. This is just with ambient shop light, the first letter carved.. Now you see it, now you don't. We are going to lay over a lauan board painted with chalkboard paint for earlier scene where they have to write on the board. will fix rods and mask with black cloth on the back that can be pulled to reveal a letter at a time.