You achieve this by going to the edge...over and over. Run your oily hands all around his penis and balls gradually building to an orgasm. The closer he gets to cumming the slower you go and decrease the pressure. After about ten minutes of this he should be right at the edge. The trick is to keep him just below cumming but at the same time giving enough stimulation that the excitement level does not decrease appreciably. It's a delicate balancing act.
The resultant intensity of pleasure can be close to that felt in a full ejaculatory orgasm but potentially unending. Furthermore, the associated sexual organs exercise, and the learned ability to better control those organs mentally, will greatly increased the scope and persuasiveness of his sexual pleasure. Feelings of pleasure are augmented by greater loin vasocongestion, and sexual organ fluid fullness and readiness. And unlike ejaculatory contractions, that feeling can last continuously, sustained for minutes on end, revivable in seconds if the attention flags. It really is a near-continuous, mind-blowing delicious orgasm! And every approach to ejaculation increases the amount of fluid held in the ampulla, with an associated increase in pleasure and passion of sexual readiness.
Another trick you might use when you finally get him to the edge point is this. You can really increase his excitement by taking each ball even more gently with all five fingertips evenly spaced around each testicle, and very gently massaging them, as if rolling an egg back and forth. No matter how desperate he is to cum, stimulating just his balls will usually not put him over, but it sure intensifies the feeling!
Step 4: The "Coup de grace"
And last but not least, if you really want to be devious and drive him crazy, you can try this little trick. Once you have brought him to the edge a sufficient number of times, and you can tell his balls are getting really full, you can take a piece of rope or a shoestring and wrap it around the base of his testicles. You may have to warm his balls up again to make them hang low so you'll have something to tie up. Making sure that it is snug/tight, but not pinching skin; continue to wrap it around and around until you have about 3 inches on either end remaining. Don't be afraid to give it a few good tugs to make sure the strands aren't loose. This won't hurt him, trust me. The goal of this phase is to separate the testicles from the body, making them unable to retreat back inside the torso. This also makes the skin tighter along the shaft of his penis, making it stand out more, as well as making it more sensitive. This also applies to his balls. There's no way they are going to escape her devious manipulations now! Starting to make sense? Finish up the process by tying the two loose ends together and viola'! With his testicles now being the center of your (and his!) universe, you now have his full attention in whatever you want to do to him. Now it is time to have some real fun!
Granted you could have tied off his balls at the very beginning of the massage and the choice is yours to make. In either case you will notice that his sensitivity has almost doubled once you begin your massage again. You can bring him to the edge again a few times if you wish but the primary objective of this phase is to give him an intense massage. The string around his balls will allow ALL of your touches to be amplified. Thus you should concentrate on his balls. You'll be surprised at the higher levels of moaning and body twitching that will occur when you massage him in this state. You could even tie him down to get complete control over him if he'll agree to it. Think you can tease him enough to get him to beg to cum? Once you decide to finish him off, don't be timid in giving his balls a good squeeze during ejaculation. You'll be surprised how intense his orgasm is, as will he. Rest assured he will thank you when it's over.