We did this with a digital camera. The same Canon 10D that I use for skydiving. This would work with any camera that can be set with a long exposure time. I think using a digital camera added to the fun because we could immediately see the results. And, the kids would build the next image based on what they learned from creating the last one.
The shutter time varied anywhere from 15 seconds to close to a minute. After I did a couple to show them how, I let the kids control it. We simply put the camera on a tripod, and set the camera on manual/bulb for shutter speed. When they pushed the button on the cable it opened the shutter. When they released the button the shutter closed. Usually the one with the light stick(s) would say 'go' and then 'stop' to the camera operator.
The early pictures were a bit more simple. As they saw the results, they became more and more creative and excited about what they were doing and after 'painting' a picture, they would quick run back to the camera to see the results.
Again, if you are a parent type of person, it was great fun.