requires stretching the skin using your free hand on the chin plus his head movements (tilt up and to the side), and thus getting the correct angle and skin tension. the chin requires the same this time pulling the skin to the sides but then shaved with many small strokes to get each facet at the correct angle and tension.

skin tension and angle of attack is the key to shaving by third party where you do not have the skin feedback to adjust to so it is less forgiving and of course the tendency is to a lighter hand when it is someone else's face.

watch an old western movie and see how it was done. 'cept the part where the guys come in through the window guns a blazin.