Each time I 'test' this using my hands I am often able to compress the artery and although the feeling each time is slightly different with different intensity, I don't feel pressure, or inability to breathe or discomfort. I tried it again right now when sat at the PC and although it took slightly longer than before, I applled pressure with my fingers and thumb, felt a very slight light-headedness - almost bringing calmness in a nice way. I then applied a bit more pressure and for a second or two felt no different but then I could feel my head slowly tilting forward, then a bit more, and more as a rush of a tingly feeling filled my head and went through my body. When I released my grip the tingly feeling stayed for a few seconds. I didn't tilt my head back or anything, I just did it while looking at the screen. I can only assume in a few more seconds I would have passed out completely.
But when I have tried with my attempts at 3D printing something, or socks, or toilet rolls. Something doesn't go correctly. I end up just getting a head full of pressure and I am unable to tighten what I am using (spoon, tie) any more without my breathing being affected, or it pinching my skin.
So, I know I only have to experience the tingly feeling and calmness, for it to work, however when using objects instead of fingers and thumb, the pressure cannot be concentrated as well so the pressure might have to be a side effect of the method. Ultimately though, feeling pressure isn't an indication it is working, or it isn't working. The tingly feeling, tilting head and calmness is (perhaps the calmness is expereinced by me because I am so under stress, but if the stress is not already there this feeling might not be noticable) what I am aiming for even when using objects. If I feel some pressure fisrst it wont be a cause to abort, but it could indicate I'm getting it a bit wrong. I'm aiming for no build up of pressure at all though which may require smaller but still soft and firm objects.