Sometimes, adding some detail is useful for filling in some pieces of the puzzle. Other times, instructors just pile detail after excruciating detail on the student and then act surprised when the person they're allegedly teaching ends up knowing even less about the subject than before. That's what most of the videos I found do: "Hey, here's a bunch of stuff you don't care about and will never use, and if you don't get it, just try harder!"
Since I try to cut to the heart of the subject, and since knowing about pendulous mounting and where the center of gravity of the compass is does you no good when you're just trying to fly an airplane somewhere, I created a pair of videos that show you what compass errors look like in a simulated cockpit. No geomagnetic theory required.
These videos are short, but the sort of thing I wish I had had when I was learning to fly. (Then again, I wish YouTube had even been around when I was learning.)
The first covers the turning errors:
And the second covers the acceleration/deceleration errors:
If there is a way I could have made these more useful for you, or you have a topic you haven't found a good video on, leave me a comment and I'll see what I can do for you.