Okay, so the principle behind that is 'Ignorance is bliss', something I'm sure you know
Essentially, the more useless things you know the longer you take to make a decision. So, you use a genjutsu to make information completely irrelevant to the fight continuously play itself across the enemy's mind (such as how much corn is grown in Konoha or something) and each time they have to
react to your move, the information keeps coming to the forefront of their minds and their reaction time severely drops.