The last time that Montag is at the fire station, he says very little at all, because everything that he tries to say is either cut short by Beatty or Faber. Beatty is speaking directly to Montag, and is very antagonistic, and attempts to put words in his mouth. He asks questions, "Where does that put you?" and then before Montag can answer he states, "I'll tell you." After his next comment he jumps in saying, "Stop blushing!" Another time Montag wants to answer but Beatty grabs his wrist saying, "God, what a pulse!". So Beatty isn't necessarily guiding his thoughts; that is more Faber. But he is sure making it hard for him to think at all by directing the conversation and being very aggressive.
It is Faber, who is speaking to Montag through the earpiece he gave him, that directs Montag's thoughts in the right direction. After each of Beatty's antagonistic rants, Faber steps in with comments like, "Don't listen...he's trying to confuse", "Montag hold on...he's muddying the waters!" and "All right, he's had his say. I'll say my say in the next few hours. And you'll take it in...and it's up to you to know with which ear you'll listen."
It is at this point that the fire alarm goes off, saving Montag, at least for the moment, until they show up at Montag's house to burn it. Before this though, he had to battle between Beatty's voice representing the society they live in, and Faber's, representing a new way, and it was very stressful and confusing to Montag.