Ok, I will share a few techniques that we use for orgasm on demand. It doesn't happen often. When it does, it is mind blowing and if you can multiple orgasm, oh WOW!

Dom should task with wanking assignments like this:

Wank in parking lot of department store until you almost come, then stop.
Wank in every room in the house until you almost come, then stop.
Wank for 15-20 minutes 4 or 5 times a day, then stop.

You get the idea. The sub should be in a constant state of arousal.

This should be supplemented by reading hot mails from dom, viewing porn, whatever else makes them hot and aroused.

Then, when play time comes, guess what? If they cum too fast, put them on the same regimen again. If they cum on command, mission accomplished.

Practice is encouraged.