I just recalled my longest ever stint at brahmacariya - about 6 (or was it 9?) months straight without (knowingly) passing a drop of seed, not even in dreams. It was before I had come to the (Buddha) Dhamma, when I was still investigating other paths, so I had to do it without
asubha contemplation, so i'm kind of amazed now, looking back. I was living in a Hindu-styled ashram, with other brahmacaris. And therein lies the answer - I was living in a community with other men who were all doing the same practice (ie, involving complete abstinence). That
was the 'secret'. So I just thought, one easy way to get one's brain off the dopamine would be to just take a few months off, and live in a monastery willing to let one stay for a period of time. You could offer to help out, clean etc. Just an idea, obviously not available if you have kids, responsibilites etc.