Yes, I suppose you have to get it just right, with enough of the wire in there to stop it backing out. I started doing it with mains plugs (in the days when you regularly fitted them yourself, and had to occasionally attend to them), because I often found them with frayed wire inside. Bending the wires down, and screwing down onto the sheath was something I always found reliable. Hard to describe exactly, though.
Yes, I'll do that if I can. Not always easy with thin stranded wire, but it means you have two screws holding the wire, instead of just one, and maybe don't need to crush so much. I once did an emergency repair on a car clutch cable with one of these, and it allowed us to finish a touring holiday. So you might say I have a bit of a soft spot for them :-)