Holy cow, I wrote a book!
I always forget how to do this, so I'm going to write it down
so I can look it up later.
When a video is playing, right-click the volume control slider
and select Enhancements, then
Play speed settings.
(Actually, it also works if you
right-click the speaker icon, the Stop button,
the Replay button, or the Shuffle button, but the volume control slider
is the biggest target.)
On the Play speed settings dialog,
the single-step controls are at the bottom; they look like
an even easier way.