learn not to shoot it out all at once, learn to edge and you can cum a bit at a time, it gets harder to cum on the 3rd try but the feeling is strong, 1st cum it will just dribble if you tense your muscle,

have a healthy diet and you will see a difference in production.

First, a daily intake of egg whites helps build your sperm production by supplying necessary proteins (you can eat whole eggs, but all those yolks are going to raise your cholesterol).

Nutritional supplements: zinc and L-arginine. Two a day, every day.

And last but most important, exercises your pelvic floor muscles all day long. Do sets and repetitions of quick flexes followed by flex-and-hold (for as long as you can). You can do this sitting at your desk at work/school or anywhere, really. And it's a very pleasurable work out   It'll also improve your sex life a ton.

I got told about this from an acquaintance who did gay porn for Helix studios. Apparently, it's a pretty widely used regime among porn stars.

And I'll tell you this, too–after doing this for a while, I noticed that I had some perceptible size increase of my penis, too. Nothing dramatic, mind you. I won't swear to you that it'll happen for you too, but I can see how improving blood flow to the area through all that PC muscle exercise could do that.

I've heard supplementing with zinc can increase volume; I take it. 

The answer to that question is dependent on a number of things, including….the emotional and sexual chemistry between you and the person you're with."

Or, as in the case of those three videos— the person you're not with.

In short, it's mostly a matter of genetics, not training.