How did Kosh's training help Sheridan fight the Shadows?
In season 2, episode 13 of Babylon 5 (Hunter, Prey) Kosh says he will teach Sheridan.
Kosh: I will teach you.
Sheridan: About yourself?
Kosh: About you. Until you are ready.
Sheridan: For what?
Kosh: To fight legends.
The period that Kosh was giving Sheridan lessons covered at minimum the time between episode 13 and episode 15 (There All the Honor Lies). In episode 15, Sheridan's lesson was experiencing a moment of perfect beauty:
Sheridan: What, you want me to go inside, is that it? Why? What's inside there?
Kosh: One moment of perfect beauty.
[Sheridan experiences one moment of perfect beauty.]
Sheridan: I had no idea. No idea at all!
The only example I can think of where Sheridan directly referenced Kosh's teachings in the Great War was in season 4, episode 6 (Into The Fire) where Sheridan quoted Kosh when confronting the Shadows and the Vorlons:
Sheridan: A Vorlon said, “Understanding is a three-edged sword,” your side, their side, and the truth. Well the truth is we don’t need you anymore!
What did Kosh teach Sheridan? How did it prepare Sheridan for the war with the Shadows?
EDIT: Radhil in the comments brought up that Sheridan laters specifically asks Kosh to teach him to fight the Shadows in season 2, episode 16 (In the Shadow of Z'ha'dum).
Capt. John Sheridan: I let him go. But there is a price tag attached. You've been teaching me so we can understand each other. That's not what I want any more. I want you to teach me... how to fight them. How to beat them. Because one day I'm going to go to Z'ha'dum and I'm going to stop them.
Kosh: If you go to Z'ha'dum, you will die.
Capt. John Sheridan: Then I die, but I will not go down easily, I will not go down alone! You will teach me?
From the dialogue it seems plausible that Kosh taught Sheridan about Shadow strategies and their psychology, though none of that is shown.