My husband died when my son was 12. I handled this kind of situation by talking to my son. The best place was in the car when we didn't have to make eye contact. He also learned that he could talk to me about anything, which is how it should be. In particular, I don't have a problem with masturbation done in moderation. I think it is a healthy way to release some sexual tension and teenagers have an over abundance of hormonal fluctuation. I really think God designed us to get married in our teens but that is not how our society works. That said, on the subject of masturbation, I simply told him that "nobody wants to see that - keep it private". To go with that, shut doors always means knock and wait for an invite in.
As for the different bodily fluids...yes, they are all the same. As a nurse, I touch them all (preferably not much [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse]) but most people do not like to encounter body fluids of other people and luckily, washing machines are useful devices that every teenager should learn how to run. [bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse][bless and do not curse] isn't any dirtier than a girls menses problems. They are natural, God made, and part of growing into adult sexual beings.