My friend Mike (not his real name) and I used to masturbate in each others presence often. In fact it was so much more satisfying with him, that I only masturbated in our sessions. He on the other hand did it by himself as well.
But since we only got together every other day or so, usually I had a bit of a load saved up and mine would always be much larger than his. One day I teased him about how big my loads were, which caused him to issue a challenge. We would only masturbate together, every day for a little while, and then see who was shooting bigger loads.
By the fifth or sixth day, although my orgasms were as strong as ever, my penis would only emit a few small streams of semen. His, on the other hand, still put out a fairly large load.
Determined to make a comeback, I started drinking lots of water, stroking myself as much as I could during the day to build up the loads, and other tricks to get my prick to fire more cum. This helped a little, but I was still outmatched.
After the second week, he was the one teasing me. I still had one thing left to try, a technique change. Perhaps, I reasoned, his orgasms were still more powerful than mine and were producing more cum as a result. The fact that I was circumcised and he wasn't, could have accounted for this. I decided I had to match the stimulation his foreskin gave his sensitive knob, to even the playing field.
I got some lotion and started using techniques that focused on the head more. This was when I discovered my favorite technique: I rubbed the tip of my penis head in circles on the palm of my other hand. This felt incredibly intense and to this day if I orgasm while doing this it's amazing. But at the time I had a load to shoot so I moved my hand aside at the very last second. From the thickness and strength of the very first shot I knew I had matched him. He congratulated me and said it was fun and it was good that I learned some new techniques, and that we should always masturbate every day (I remember him saying 'if you go a day without shooting a load, you definitely didn't use your penis to the fullest').