I tried Semenex many years ago back at Uni. At the time the advert was saying you could cum like Peter North. I took the pills for a month and only noticed slightly more seminal fluid (this did not visibly increase the spermoza (white swimmers)). While it wasn't scientific with measurements it wasn't anything near double the load, more like 10% increase in semen and I certainly didn't shoot my load, there was no difference. I also tried zinc supplements but this didn't work for me either. I was in overall good health and had a good diet (not like a fitness guru) and stopped taken the semenex and zinc pills. Everyone is different and these didn't work for me.

I have been able to shoot a couple of shots (about 3-6inches) and this has been:

1. Being very aroused. If you watch a lot of porn for many years then it becomes samey, which does the job for a "quickie". But there are a few vids you'll find, which are different (newer level of dirty) and give you that extra something.
2. Building up for a long period. Going "hot" and "cold" during the day helps and work the PC muscle. I've also found that just in the session (an entire porn film and not just 5mins) building up and holding works. This also helps me lube up the internal plumbing (mentioned in an earlier post) so that cum comes out easier.
3. I've noticed that when I do shoot and not dribble my semen/precum acts as a cork on my penis tip.

Hope that helps. I've started trying some supplements. Will see if they make any difference.