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Personally I would use adult entertainment but that's because I enjoy masturbating to adult entertainment. If you have a personal, moral, or religious, or any other reason to not watch adult entertainment then don't watch adult entertainment. You can improve [words=http://fleshlight.sjv.io/c/348327/302851/4702]stamina[/words] without it.
Beyond that the visual simulation of adult entertainment will bring most people to orgasm faster. Just for fun there were times I sat naked watching adult entertainment and tried to see how long I could watch before masturbating. When I finally did masturbate it didn't take long before I was ready to cum. Personally I would start off with a [words=http://fleshlight.sjv.io/c/348327/302851/4702]Fleshlight[/words] and no adult entertainment for a while, then add in adult entertainment.
A fun technique for masturbation is to use a clock or a timer that you can't see the seconds, just the minutes, and set a time of 10 minutes and do not cum before that time is up yet try as hard as possible to continue masturbating through the whole thing. It really builds anticipation, which you have during any sexual encounter anyway, and forces you to go a certain time. This can be done with or without adult entertainment (I prefer with but that's just me).
There's plenty of other tricks and exercises you can use and a lot of them are fun at the same time.