Back when I was a horny teen and used to jerk off all the time, and look at porn with friends. On more than one occasion we would jerk off together, never touching each other but both of us stroking our cocks until we came.
When I discovered jacking off and cum, I was maybe 12 or 13 and I was at a friends house and there were other boys there. I told them about it and they wanted to see. So, I took off my pants and jerked for them. First, they couldn't believe my cock (it's always been big) but when I shot my load I thought they were going to fall over.