My husband likes to do this with me. He simply puts his hands behind my head to cradle it and reaches up with his thumbs to push on my arteries to cut off the blood flow. He watches my face very closely while he is doing it, and I don't fight him on it, so the second I want let loose, I simply slap his back and he lets me go, and if he doesn't like my facial expressions, he'll let go. I've been close to passing out, but never actually did because he'd notice my inability to respond to him in any way.