I believe you would lose your senses relatively quickly and peacefully pass out.
It should be painless. I have experimented the same technique in a different way, it works surprisingly well and it even feels good. I did it to myself using a belt and didn't Ctb because as I fainted I lost grip and the blood started running again. It feels pleasant, I assume kinda like you're high. Your brain will trip and you'll think you're living a million things, untill it goes black. Do you know the sensation of being just partially asleep? Thats it.
Truth is if your brain runs out of blood, you'll simply faint.
After a few minutes of being passed out, if no one finds you and your body doesn't have a way to pump blood to your brain you'll be brain dead.
Easy, simple, painless and quick.
Very probable that That's going to be my way of Ctb'ing.
