One of a few guy/guy masturbation experiences I've had.
The story about the guy and his college roommate humping each other's butt cheeks is similar to an experience I had when I was in college. I did my junior year in England and a friend of mine from home came over for spring break and we traveled in Europe together. One night in Paris we ended up in a cheap hotel having to share a none-too-large bed. Early in the morning I woke with an erection, which had poked out of my boxers and was touching my friend's butt. Once I realized what had happened I quickly rolled over onto my back and hoped he was still asleep, but he wasn't, so I just said that I was sorry I had a "morning woodie." He said it was ok, and that he had one too. He then rolled over on his back, and we both could see our erections tenting the sheet and I watched as he stroked himself a couple of times under it. I'd never masturbated with him before (though I had with another friend once when I was about 12) but I was suddenly turned on, so I began stroking myself too. Soon we were both really into it. I could see both of our hands moving under the sheets and our bodies moving around, and hear the sounds our fists made on our penises as we pumped ourselves. We were both looking at our fists moving up and down under the sheets and then at each other's faces as we did and I remember my friend getting this huge grin on his face before he came and then closing his eyes and arching his back .as he orgasmed. He lay still for awhile but rolled over and was looking right at me when I told him I was close and then came about thirty seconds later.
We lay around for a while in that post-orgasm haze and then started talking about jerking off and the times we'd done it with another guy before, and he told me that he and a friend had actually done it to each other. I asked him about that and got pretty turned and I asked him if he wanted to do it again and he said yes. My friend took off his boxers and tossed them out of the bed, so I did the same and we lay on our sides facing each other and both reached for each other right away and felt each other harden up. I was clumsy at first and was just feeling him rather than trying to stroke him, but he put one hand under my balls and wrapped the other around my penis and gently started to pump me. It felt so good I just did the same to him and we stroked each other like that for a couple of minutes. I thought we would have orgasms like this, but my friend then scooted right up against me and then spitting into his hand and wiping it on our penises and told me to do the same. It was kind of gross but felt good so I got a bunch of spit and put it on us and he took both our penises in his hands and held them together. I got the idea immediately and began to thrust my penis through his hands and against his penis. Our saliva made us really slick and it felt really great so we did this for a minute or two then my friend asked me to get on my back and he got between my legs and we slicked ourselves up with more saliva. He then leaned forward and put his elbows on the bed on either side of my chest and holding himself over me, put his penis against mine. This time I put my hands around us and he started to thrust. As soon as he got going he pushed himself up on his hands and the sheet slid off down to our legs and it looked like he was having sex. He started to really thrust into my hands and I raised my knees up beside him and started rocking my hips against him. The feeling was so good, but I'd come just a little while before, and we had to stop a couple of times to slick ourselves up again, that I was able to last for about ten minutes before I came. My friend stopped for a few seconds while I kind of squirmed around while I had my orgasm then started going again for another couple of minutes before suddenly stopping and then sort of jerking back and forth as he came.
We did this two more times over the next couple of weeks, but we usually were staying in hostels so we didn't have the privacy for it. We both attended different colleges, so we didn't get to see each other much, but did do this one more time about a year later when we saw each other over Christmas. After that, we both ended up in different cities, and though we've kept in touch and seen each other a few times, we haven't done it again.