The problem with instructional lather vids is that... virtually none of them actually show building lather. I've seen about one and a half vids on YouTube that show the actual building of the lather.

In one video, the camera is only on the bowl & soap, but he uses some concoction of "locally handmade soap" that looks like chunks of lard, and an oil from a local plant. The lather produced (likely meant as an overview/quick demo of how-to) was mostly huge bubbles, like you would see washing dishes. Outside of those issues, it was a decent video.

Face lathering vids don't really count, either. They very rarely show how this person is building the soap on the brush.

Also, there don't seem to be any vids showing examples of how it goes wrong. Like too much water, overworked lather, the difference adding glycerin makes, how much time it takes a lather with not enough water to dry out once applied to the face.

The camera should basically always have the brush in the shot. Maybe a wrist mounted GoPro?

If I weren't a noob myself, I'd make one, or six, of these vids. I, and surely other noobs, welcome useful submissions.