Can't really see a need for this, but if I had to hazard a guess I'd say (1) wait 3 to 5 days between ejaculations and (2) masturbate / have sex a lot in the build up to your desired shooting and get close to orgasm but don't go over the edge for an hour or so.
And possibly (3) gently squeeze the base or shaft of your penis at the point of ejaculation; this squeezes your urethra and should make you ejaculate further. Don't squeeze too hard, this might block anything coming out.

Let us know how you get on...

Will give it a shot...haha I will let you know if that works...
THANKS!!