I love the power of being able to make a man jump like that, sucking all of his cum out and running my tongue under the head where it's really sensitive. I just dont stop sucking until he is cleaned out and licked off.
Obviously your girlfriend is willing to give you pleasure, something that you don't think is very common... so you have to teach her... once you release the milk she has to continue sucking but at a gentle pace and not leave her head outside the foreskin, because otherwise it's unpleasant... that way you'll have an incredible minute-long orgasm!!!... When the cock loses rigidity there, if you stick the head out and clean up if there's any milk left... This is how my wife does it with his clients... and with me obviously.