Channel that detects black moving pixels:

Layered the moving particle channel over the live feed:

It was a nice visual but I felt it could be better.
Perhaps it gave a lightness to the image, but I thought the layers were a little detached.

It finally dawned on me the day before the presentation, that I could simply invert the black-and-white alpha channel and allow the moving particles to be black like my hair instead! The answer was so obvious I was focusing so much on coding I fail to see it!

This is the patch with the resulting image:

The hair visualisation blends in nicely with the live feed but also takes on a life of its own.
The pixelation adds a lo-hi quality to it and breaks the illusion of it being a CGI image.

During the performance, I set the webcam at face level to grey-scale in order to contrast with the white and blue lighting captured from the top camera.