Haha, so funny. I think you've all kinda misread the original post.
He was talking about overhead projectors. Most certainly using a tungsten/halogen bulb.
I think you can easily do this by creating two layers, one for each overhead/channel. Then create solids with a certain size somewhere in the comp (make two squares of 30x30px one left one right, does not matter).
Then, turn ON the bypass switch of those layers. So these squares won't end up in your final comp.
NEXT UP, you go to the Advanced output window and make two fixtures, just a simple 1-channel intensity fixture.
You can set the 'input' of this fixture to a single layer. Pick the layers you've just created. Just lay the fixture over these white squares and you're good to go, right?