Thinning a knife, for me, is not easy, in fact it is quite challenging.
Please note that I did not go to Sharpening University and get a Masters Degree in Thinning. This comes with a lot trial and error and mistakes. There are different approaches to thinning and this one in the video is quite new to me.
In the past, I was thinning at a less acute angle, just a few degrees less than the sharpening angle but now I thin at a much more acute angle. The problem with this is the scratching of the blade so be aware, if this is something you plan to do, you will scratch your blade. Yes, you can polish some of them out with high grit stones but it won't get rid of all of them.
I use wet/dry sandpaper on the scratches myself but some people use a belt system with special conditioning belts, I don't have any of those yet but I do know it is possible to restore the finish of a scratched blade with them.