Warning: this takes tremendous mental discipline and will-power.
i think this is a common method prob practiced by some of the senior bros here:
the moment u feel like an ejaculation coming on, cease everything and think of mother teresa
(or better still, lee kwan you) .. let the feeling pass.. control.. endure.. after the feeling has passed, resume last action.
Repeat steps for at least two other times and u shld hv a bursting tank to fire away !