I think a lot of it would start during pre-production planning and shooting. For example, it will be easier to separate areas of light and shadow if there is more contrast between them. Consider running some tests with a low-key lighting setup with a high key to fill ratio.
Once your test footage is in AE I would look at the Layer > Auto-Trace tool, which is basically a Live Trace that can be applied to the entire length of your workspace. Here’s some info from Adobe’s exhaustive help files:
https://livedocs.adobe.com/en_US/AfterEffects/8.0/WS65568770-F022-4c7e-89F4-AC9F2E563386.html
Using the luminance for the Auto-Trace is a good place to start, but you could also look at each RGB channel of your footage independently and use one that more closely approximates the contrast you require.
You will want to apply the Auto-Trace to a new solid layer (an option in the Auto-Trace dialog) so that the masked areas correspond to areas of solid color instead of the RGB of the original footage.
The other note to add to this is that you should consider doing several Auto-Traces at different thresholds to develop a more posterized black-to-gray-to-white look. Off the top of my head, if you were going to use 3 shades of gray I would think to try auto-tracing with well distributed thresholds like 230, 200, 170. Then set each of your Auto-Traced solid layers to 33% brightness and use an additive blend mode (Add/Screen).
I can’t stress enough how important it will be to run some tests of the workflow though.
Darby Edelen
Designer
Left Coast Digital
Santa Cruz, CA