Just to be clear--that video shows the simple technique to align the caliper, it will not straighten a slight bend in a rotor.
As in all things in life, you can watch YouTube videos or be told how to do it, but straightening a rotor takes a certain amount of force, and specifically finesse in the force you use, and duration of force.

No matter of reading will teach you the real world force needed to do it
As always, start with less force and work your way up, observing how the rotor actually responds.

Online stuff is only that, and you have to have the ability to learn as you go and adjust the hands on side of things. Gradual increases and how you force is key.

You'll only really learn by doing it.
This video does not show straightening an out of true rotor.
But rotors are pretty tough, you'll be surprised how hard you have to put pressure--but not all on one shot.

That said, some folks have a lot less skill in doing hands on stuff, or learning/ observing -- that's the kicker.