Keep in mind that there were agents like Agent A-KO (probably more), whose main mission was to send back personality profiles of the higher ups specifically to find those fault lines. So that, when the time came, Largo knew not only which buttons to press but where they were, how big they are and how hard to press them. I would think that Largo wouldn't run the risk of doing any direct manipulation like telepathy/psychiatry because the more you try to influence, the greater the chance something goes wrong. With all the agents that infiltrated the WDF to execute the observe/report mission, he wouldn't need to do any shaping. He already knows how to break them.