There is a book by some female author that teaches the technique (for men.) I can't remember the author or the book title, but basically dingdongbell is accurate in that by building up the strength of the muscles that control the urethra during urination, and then tensing those muscles at the time of ejaculation, the ejaculation would be "dry", and the erection would continue.
Now, a while ago, I did the training regimen and attempted to use the technique. The bottom line for me is that it never felt right - the ejaculation only feels right if the tension is relieved. By coincidence, I have prostate problems (a narrow urethra, like Hank "King of the" Hill), and have taken various medications for it. I tried the Flomax once, and it caused a similar response; I hated it (BTW, Hytrin is a much, much better medicine for the prostate - kind of like Viagra!)
I think it is much better to be able to shoot a load and then reload quickly to shoot again, than to simply stay hard. Remember, women really want to get fertilized, not simply have a hard penis in them. Men get the physical thrill of ejaculation, but women get the psychological thrill (that they have been able to satisfy their man.)