It's actually CGI, he's really a quadriplegic who's into video editing and creation. If you look closely the blue sweater is actually a blue screen effect, we painted his puff powered wheelchair blue and CGI'd in the sweater and gun, and working arms. His head ducks so low because he has no muscle control in his spine and can barely keep his head up at the best of times.
While it's cool to call it the "Slavex Method" (and that is now copyrighted), I learned that method of decocking from Nick King. I've DQ'd a number of people doing the Pinch method, or the thumb on the hammer lower, and seen many many ADs at my range and others using those methods. This, in my opinion, is the safest way to lower the hammer. I have big meaty hands too, and have to pay careful attention to the roll out of my thumb to avoid the hammer snapping that last little bit. But it's never a race to decock, so take your time, the pinch and thumb on hammer method work great until your hands are sweaty or greasy, then, BANG. Although so long as you are pointing in a safe direction you will be fine. And far too many people get lackadaisical when decocking, and allow the muzzle to point up, way to high up, or to the side, or anywhere but straight down range. Drives me mental (and I've done it too, which drives me more mental).