If you do any sort of #Electronics work where you have to strip tiny wires of 20 AWG or less I highly recommend you get yourself a precision wire stripper.
I've found that a finger nail or thumb nail works great depending on the thickness and hardness of insulation.
E.g., pinch the wire between your thumb nail and finger then pull. The thumb nail isn't strong enough to cut the wire but if the insulation is thin it will pull off easily.