In my opinion, an underrated aspect of elite coaching (which I'm subjectively defining as coaching in the first division of top European leagues) is the methodology. In particular, I'm speaking about a coach's exercise selection.
All we get to see as outsiders is one tiny piece of the puzzle: the games. And maybe we can even discern that a certain plan has been put in place, perhaps to press the opponent in such a way that the worst passer is on the ball the most, or to match up the best attacker with the worst defender. But we don't get to see the real work that goes in to this.
Sure, we can see Barcelona do a 10v2 rondo, or watch Pep shout in German at camp in Qatar... but we don't get to see the training sessions leading up to an important Champions League knockout game, or see the first 10 sessions Antonio Conte does during preseason. With some digging, you can find worthwhile content on the internet. These are three of my favorite from Simeone, Bielsa, and Frans Hoek.
What I am getting at is this: the best have a refined methodology. I sincerely doubt that Mourinho has 50 different drills to train his teams to counter attack. I'm willing to bet he has a set of core exercises that he tweaks based on the players, the opponent, the conditions of the match, etc. He's probably not reinventing the wheel every time he moves clubs. And his exercises are different than Jurgen Klopp's, and Pep's, and Van Gaal's, and Allegri's, ad infinitum. What separates those guys from each other is their ability to analyze their players and the opposition in detail, and assess weakness, strengths, etc.
For now, I feel like I'm still in the stage of dialing in my methodology. Which exercises I use, for how long, the specifications, and the sequencing, to name just a few aspects. 3four3 has been helpful with that for me personally. More than anything though, find a working method, and relentlessly study and refine it.