Well, first of all be very careful about what you believe in YouTube videos. That's just a general warning across the board. YouTube is a minefield and if you don't know if what you are watching is accurate or not then you can get sucked in by some BS artist and if you DO know if it is accurate then you probably gain nothing from it anyway.

Here is a video from an instructor that I personally recommend.

https://youtu.be/63cNUU206-0