I couldn't achieve a satisfactory result doing live screencasting commentary. Neither the execution nor the commentary was adequate, and it was draining to perform. Asynchronous and discontinuous proved superior.
Pausing for mini-breaks improves execution and reduces fatigue. Camtasia has a pause indicator in the MacOS menu bar. Fullscreen apps obscure this bar, so use maximized instead. I didn't find a way to move the pause indicator off the menu bar, so this is a must. The pause indicator makes pausing much smoother.
Rely heavily on '3dashboard to manage execution and screencasting tasks.
Live commentary is for live streaming. Otherwise the decline in commentary quality due to lack of foreknowledge isn't worth the extra emotional immediacy.
Performing post-commentary is boring at 1x speed. At 1.5x, it becomes an interesting opportunity to review execution for strategic mistakes, and to offer asides during lulls. The delayed review accelerates learning. Silent execution is more skillful, and review commentary grasps the big picture.