I like the diagrams, as many explanations often skip the staging portion of the whole git process. I use that so much that it baffles me that most people skip it. Then again, I typically don't like having tons of "WIP" commits so I stage a lot and if I need to switch to another branch I'll commit a WIP that I quickly `rebase -i` to get back to a clean status.

As for the teaching part, I have found the best results by having you and the learner actually "working" on the project at the same time on your own machines both pushing to a centralized server. It becomes too easy to go over all the commands and feel like you understand it. Most of the scary parts of git are used when its multiple developers on the same project. And oddly enough, having the learner do both Developer A and Developer B's tasks don't seem to work as well as having the learner just do Developer B while I do Developer A. Trying to explain to someone when to use merge, when to rebase, and when to use cherry-picking to get the code I just pushed into their current working branch can be done so much easier when its hands on AND knowing exactly who is doing what steps.