De-glazing cylinders

[Ben]

I've just had a go at de-glazing my cylinder walls. I've watched quite a few YouTube vids first to try and get the right technique, and I think it went reasonably well.

What I didn't get from the vids though was how to know how much pressure to apply. I've de-glazed on the lowest pressure setting on the tool and its de-glazed and left score marks (although no where near as diagonal as before), but should I then tighten the tool and do it again?

Also the majority of the score marks are good, but there are a couple which are more obvious, and you can feel with your nail a little easier. Is this normal?