Hard to say any specific anecdotes for how he does it. It's mostly in attitude; how he says things rather than what he says. You can tell from his attitude that when he challenges you, it's not to put you down or exert authority, it's because he genuinely wants everyone to come to the strongest conclusion. (Even if most people think they also act this way, probably they don't, or they don't express it that well).
There will be a discussion that starts meandering, going down rabbit holes, and somehow he'll find the perfect question to ask, which is always a very simple one, to set everyone back on target. Sometimes I don't think people even realize this is happening.
The reason it's hard to explain is because it comes across as an innate character trait, a skill that's just core to his personality, which is why it's so hard to emulate.
