I've never had any male masturbation buddies. Only few female friends were masturbation buddies. My first was when she and I were teens. Oddly enough we never had sex with each other until we were in our early 30's.
In my 20s I had a friend who slept over in my apartment. We watched each other masturbate for a few years. On a few occasions it went a bit further. He would rub my cock and I'd rub his. We had oral sex a few times and swallowed cum.
I didn't when I was young, but have had some in the last 10 years. I'm 61 now. Generally we start by watching porn, then lowering our pants and underwear. It's fun talking about the things we like about the women in the movie... her looks, body, etc. Sometimes we end up stroking each other.
Just an update on my post above. Was looking at things on the internet and some urban explorers had been in my old school, which was small and in the centre of town and now sadly quite derelict. It reminded me of when me and my wank buddy would break in to the school at night. There was one particular place that was easy to enter and no alarms or anything. So we would get in through that window then immediately get naked and stack out clothes neatly on a shelf. We would then casually walk around the about 15 rooms accessible from there completely hard of course. We would usually have a quick wank and short suck in every room eventually deciding to make each other cum at some point. Cum locations included head teachers office , staff room and the desks in our own form room. The last was quite risky as it would have been possible for someone to look in. Sometimes after we got dressed to go and left that block we would have to stop off for a wank or suck in one of two other places in the school as we were so horny.
As a kid, I used to masturbate while my mates sister and her best mate watched. I was maybe 12/13 they were a little older, but not much. As an adult. When my wife goes out with her friends. She will sometimes bring one or two home and ask me to give them a show.