I think some people are having a tough idea envisioning this, so here's my research on the subject. This method is a physical way of depriving the brain of oxygen, hypoxia, versus an inhalation method using CO, Nitrogen, or Argon. The result and effects are the same, brain death occurs in less than 5 minutes, sometimes as quick as 2 minutes. The night-night method is a fairly quick shut off of the process so the sensations of euphoria, tingling, and grayed out vision occur much quicker. The uninterrupted flow of blood to the brain deprived of oxygen through gas inhalation is a little more subtle and symptom onset probably a little slower but not by much. Both methods of hypoxia to the brain are absolutely lethal if done properly. Both are virtually painless, night-night involves more pressure applied to the neck.
The OP has done an excellent job of collecting information and sourcing. It just seemed liked people were unsure of how this method worked physiologically. Hypoxia methods using gases and this, are probably two of the most humane methods we have available to us. Read through the thread again, all the information and answers are already there for you.
We're not depriving the brain of oxygen. We're depriving the brain of over 90% of blood flow. If we were doing an air choke, then we would be cutting off oxygen. With the blood choke though, we're physically killing the brain off faster. Yes, I understand that we're taking away oxygen that is in the blood. If we want to get even more technical, we should think of the NN more as stenosis of the carotid arteries.
The brain needs blood to function at all. To put up even more fancy terms, think of the night-night method more as embolization or even as a tourniquet with padding. We're cutting the blood flow to the brain. When done properly, brain death can be even faster than 2 minutes. You won't know though, as you will pass out in less than 20 seconds, if not 10 max.
As for the pressure, when you're doing it correctly, you'll notice a slight pressure and then that's it. You might become a little dizzy and then it will hit you. Blackness. After that, the brain will lose too much blood and oxygen and you will experience brain death.
The pressure might freak you out a little if you haven't practiced before, but if you haven't practiced before, then you run the risk of messing up the attempt. Like someone shooting at their chin with a shotgun. It's not going to end up well. You might still die, but it might mess up and end up being extremely painful.
As for the ratchets with the hooks, that will still work as well. It just might not be as comfortable. If that's all you have access to though, don't be discouraged at using it.
I do greatly appreciate you telling everyone to read through the thread again though. As I've had to say it far too many times already.