Looking online, it seems that most people do not do a ruined orgasm. From experimenting with my husband, I think I know the most effective way to do it.
First, I think the best ones include no stimulation of the shaft. That is a personal choice. The reason that I say this is because men are used to the shaft being stroked. The mental part of no stroking of the shaft is important to changing the feelings that they have. I prefer to rub the area between the balls and the anus. At first, I am much rougher. I can see that he struggles with not telling me to stop. After a bit of that, I back off and massage that area less roughly. Another important part is that they must ask to orgasm. You can try and see every twitch but it works much better if they need to warn you well in advance. Once they begin warning you, stop stimulation and wait. Give then 30-60 second breaks and then restart. When I am doing the best, he begins thrusting his hips into the air. Try and get them to settle down and be less showy. As they feel the need to orgasm, keep edging them closer and closer. At this point, what you are trying to do is get one big drop of semen on the tip. As soon as you get this, stop stimulation and the session is over. In future sessions, you can push them a little further. The goal as I see it is to have them orgasm just a little about 30-60 seconds after all stimulation is removed. When I've asked my husband about this, he says that he fights against the orgasm but at one point, he has no ability to control things and the desire to cum just overwhelms him. With stimulation removed at just the right time, that sensation leads to the smallest of semen releases. He is hornier than ever after I have done this. This is why I think cock cages are important as it is doubtful that most men can control their urge to stroke to orgasm. Eventually, my husband learned to like this form of orgasm so much that he almost didn't want a full orgasm. This is because he was getting attention from me every night.
I hope this helps.