Here is an example of how I will do a basic run though of a scene between two characters.
This is from "The Devil and Daniel Mouse" (1977-78). Jan (the female mouse) is dejected and saying, "Maybe we just better quit," as Dan walks alongside her, switching his guitar case from one hand to the other.
Thumbnailing a scene like this is more than thinking about the posing, it involves how to think through the characters' particular timing so that they have a different energy, even if only slightly so. Being able to see the timing charts alongside each other is like seeing the music bars for two different instruments that are playing the same piece of music, but are accompanying each other, not playing the same notes with the same emphasis.