OK, you can kegel during masturbation/sex to speed up the point of no return. Squeezing the muscle a lot during masturbation/sex can bring the ejaculation on really, really quickly. Obviously if you wanna take ur time, don’t tense it a lot. When you feel da point of no return coming you THEN completely relax, and squeeze the BC muscle hard, and hold. That’s how I do it any way. You can squeeze it as much as you want really (it can be quite enjoyable), just as long as you’re able to squeeze and hold it long and hard enough to keep your cum in.
If you want to be REALLY multi-orgasmic (as in more than one orgasm in the space of seconds), what I do is hold it in by squeezing muscle, I stop the friction for 5 seconds while I hold, and then start masturbating/pounding again but QUICKLY tensing and releasing the BC muscle, until you feel the point of no return again. You then HOLD for 5 seconds while you stop the friction, and then start pounding again but tensing and releasing da muscle real quick till you feel da point of no return again. Repeat indefinitely :)
As for your second question, personally I think squeezing the tube wid your fingers is cheating. Further, sometimes the cum WILL come out into the tube, and because your squeezing it it’ll go back in and into your urinal system. You’ll go limp, because you DID ejaculate - it just went into you, instead of out of you. This is perfectly harmless, other than making you really wanna pee :) In my opinion, keep training the BC muscle until you don’t need to squeeze with your fingers.
G’luck :)