Stop just before you reach the point of no return the point where you would ejaculate. Contract squeeze and hold your PC muscle for a count of ten. Every so often the first one is pretty "meh". This will help the body assimilate the energy from the testicles to the rest of the body. If you have no trouble reaching singular orgasms either by yourself or with a partner, then learning how to become multi-orgasmic may only be a matter of patience, determination, and effort.
You'll probably feel yourself trying to ejaculate, but hold it back!
How Men Can Have Multiple Orgasms
If you squeeze or contract the PC muscle you should feel like everything deep in your pelvis is being drawn upward. Yep, I can vouch for multiply orgasmic men. If you are successful, the contractions will stop before you ejaculate and you should be able to resume stimulation without a loss of sensitivity, as would be present during the refractory period after ejaculation. Contract squeeze and hold your PC muscle for a count of ten. It is actually physically possible for you to reach climax more than once before you ejaculate. Allow yourself relax and take a few minutes break.