"But I would watch him and he'd say the most poetic things, like, 'You do not kick the bar, you lean into the bar because it's not 'Vino Veritas, it's In Vino Veritas', he'd just spout all these things out and I put them in the movie."
And Nicolas - who won an Oscar, a Golden Globe and a Screen Actors Guild award for his performance - admitted there were some scenes he shot while "completely hammered" because he wanted to be as "credible" as possible.
He said: "It was a four-week shoot - thank God it was a only four-week shoot - because there were a few scenes where I wanted to be hammered.
"Because I wanted to be out of control and have them photograph that so I could reach that credibility, that authenticity.
"The scene that comes to mind is the casino scene, where I flipped the table and had a blackout because I didn't know I was going to go there, I just wanted something extraordinary happen and they kept it in the movie."
And on another of his movies, 'Bad Lieutenant: Port of Call New Orleans', the actor took to carrying around a vial of "saccharine substitute" that looked "like coke", much to the astonishment of director Werner Herzog.
He said: "I'd try and snort this and get into the headspace. Werner and everyone's getting a little flipped out about my psych-up process to get this scene because I'm going nuts and high on 'coke'."
And even when questioned about the 'cocaine', he refused to break character to reassure his bosses.
He continued: "Werner said, 'Now, Nicolas, what is in that vial?' This is right before action, I don't have to say it's not coke because it's gonna break the imagination, I'm psyching myself up - I was completely dry on that movie - but he broke my concentration.
"I [shouted in character], 'Coke! Now get off my set! Get out of New Orleans! This is my city!'
"Then they said 'Action,' and I was the guy, I was in that headspace."
