Talc in Motion
I mounted the bottom brush in a vice, and placed a bit of talcum powder on it. I flicked the top brush with my right hand, and triggered the remote shutter with my left. Took about 100+ shots, and found the one I liked best.
I used a camera-mounted flash as the only lighting, and used a white card to direct the light toward the brush. I set the flash to a lower power (1/16, I think.) The lower power results in a shorter flash duration, which stops the motion better. Kept the room as dark as I could.
Stopped lens down to f/11 to get a reasonably wide DoF. Shutter speed was 1/250s, though the speed is really controlled by the flash, rather than the shutter.
Processing was fairly straightforward: Adjusted RAW levels, cropped, resized, unsharp mask.
That was a lot of fun to shoot. (Though there were vast quantities of powder coating the room afterwards :) ) I'm really pleased with how it turned out.