I was going to say what Pecker said. But Pecker said it. So I won't.
I have clients who routinely have a (skilled and practiced) dominatrix inject saline into their scrotums. They say it doesn't hurt, there's a lot of pressure, but no pain. They say it is very uncomfortable to stand at first, but then they end up in panties, which are apparently very supportive, anyway. To my knowledge, they have no need to produce a oceans of jizz, and don't get into the pornotastic special effects. If I ever talk to someone who does, I'll let you guys know everything I find out!