@daime17, Joke answer: The dad brought him to a brothel. XD
Serious answer: Probably just linguistic advice and tips, like "Son, woman like to be touched here and there" or "You see, the trick in pleasuring woman is to do this and that" during their father-son time (the time between the father ditches his previous victim and search for next could work too). The son probably has good memories and natural talent to boot that he could do all of his dad teaching effectively in practice. As for the question of "Why the heck a father shares something like that to his son?", well... they say parents like to have their children to continue their legacy?