I used to have common sleep paralysis which sounds like the author's experience (sans the "demon", which definitely sounds like an improvement). I don't really remember if I could feel or not. A method I learned online (I've since forgotten where) that works even better than the finger-wiggling method is to try to hyperventilate through just your nose. Not sure exactly what's going on but I have a guess it's tricking your brain into thinking you can't breathe and so it wakes you up quick.