If I really used Weit Liaozi to explain the military situation to Zhang Fei, Chen Xi estimated that even if Zhuge Liang possessed him, he still wouldn't get through to Zhang Fei.
As for the pre-battle prep, battle planning, and post-battle reflection covered in those three points, it didn't matter whether Zhang Fei understood them or not. Just doing as told would be sufficient. Military strategy, once taken to the battlefield repeatedly, would eventually be comprehended, progressing from learning to understanding, and from understanding to transcendence.
After all, Zhang Fei was to practice against the Hu People, not Cao Cao. Even with bonuses like famine or fighting to the death, it wouldn't be too difficult. As he fought, he'd get the hang of it and naturally handle it well then.
Although Zhang Fei didn't understand these things, he still rigidly memorized them. As for comprehension, that would be a matter for the battlefield.
