Then slowly bring down the hand that's on top to the base. It is sort of milking it in a downward motion. Make sure that the pressure is just about right, not too tight, and not too loose.
When pulling, do it with just the right amount of force. Too much pull and you risk damaging the nerves in it. Also, when doing these exercises, it is important to avoid getting full erection because otherwise, it wouldn't be as effective.