THIS LPT IS DANGEROUS. DO NOT FOLLOW IT.
What the article suggests is hyperventilating. That's a VERY bad idea.
See, what lets your body know you need to breathe is -oddly- not the lack of oxygen, but the excess of CO2. In other words, if you lower artificially your levels of CO2 (which is what the OP says in point 3), you're tricking your body into thinking it doesn't need to breathe, and you might lose your consciousness, without even realising you needed to breathe.
If this happens out of the water, chances are you'll wake up later wondering what happened.
If this happens underwater, and nobody's there to help you, you'll drown. When you're freediving, you'll have your lungs full, so your body's first reflex will be to exhale all the air in order to breathe. Underwater, empty lungs=negative buoyancy, so you'll start to sink, and the person watching over you has a very small window of opportunity to realise something's wrong, go get you, and bring you back to the surface.
If you want to learn how to hold your breath, it's very simple: take a freediving course, and practice a lot (and never, ever, alone, always with a freediver able to go to the same depths as you)
I'm a commercial diver
I've been freediving for many years
I've worked with several world champions
I've experienced a blackout myself (I had people next to me, so I was never in danger but I know first hand that you really will not see it coming)
Several -very experienced- people I've known over the years have had accidents, sometimes leading to death, while freediving.