Hasta La Motion!

I am looking for a trick or tutorial that shows me how I can create a grayscale or alpha smoke matte from actual footage.

Imagine video footage of something, and then there’s smoke entering the screen. Because I want to put a layer underneath the smoke, I think it should be possible to extract just the smoke.

In theory, I think stabilizing the footage and using a still from before the smoke enters the screen to ‘calculate’ what is smoke and what is back plate might work. Sort of like a difference key, except the smoke is supposed to be partially transparent.

Any ideas for an approach or does anyone recall an article or tutorial about this?