I originally set up a front projection system in my classroom with only one Wiimote and I found I had major tracking issues and it was difficult for my students to understand they couldn't block the camera in the wiimote. So I decided that I wanted to make a large rear-projection screen set up in my class.
At first I had trouble finding information about this set up. It is more time consuming to make so I assumed that is why it not commonly used. Originally I tried what some others had done, trying to use frosted glass or plexiglass but I got really poor diffusion. I also tried the Frosted shower curtain approach which also gave poor results (hot spotting).
I finally decided to spend the $37 dollars on actual rear projection material. And the results blew my mind. I then built a frame and support legs with wheels for my screen, all in all it cost me about $75 - $100 including the screen material. This is by far the easiest to use and explain wiimote set up and my students love it.