How much should you write before recording a short tutorial?
[cue pause]
Start with three things.
The question you are answering.
One example that makes the answer clear.
And the next thing the viewer can try.

If your topic is better lighting, show one camera angle before and after moving a lamp.
[cue show the comparison]
Explain what you changed.
Then stop there.

A clear example gives you enough for one useful video.