I had seen this technique a few times and I have wanted to reproduce it, but was always wary of doing it with film. Now that I've got an DSLR, I figured I'd give it a shot.
My wonderful wife laid on the couch to be my model / test subject. I set my camera to f10 @ 30" using my 28-80 at around 50mm. I took my flashlight and covered it with wax paper to diffuse the light since a Maglite isn't the most focused and even light around. I turned out all the lights in the house and hit the shutter.
I proceded to "paint" the light over Kari, ensuring that the flashlight itself was never seen by the camera (I uploaded the goof shot where you can see it in the upper right corner). You have to keep the light moving so as to not burn out the photo. 30 seconds is a long time, but you could always set your camera to bulb mode and go longer if you need.
This photo represents the very first shot I did with this, and I think I got a pretty cool effect. Now that I know I can do it, I hope to try quite a few more portraits using this method.
