The Breaking Bad star told Reuters that the most authentic way for him to play an alcoholic was to observe his own drunken behaviour.
"There's nothing worse than seeing an actor trying to play a drunk and it's just so obvious that it's acting," he explained, adding: "I was excited about that challenge."
Paul further explained: "I drank heavily and my friends filmed me. I wanted to make myself look like I had a problem."
He went on to discuss what he learned when watching the footage.
"It's incredible what alcohol does to you; after each drink, you truly change quite a lot," he noted. "I'm definitely a happy drunk. I'm very loud. But it was somewhat painful the following day."
Paul stars in Smashed with Mary Elizabeth Winstead, whose character's own alcohol problem leads to disastrous consequences.
Smashed is now playing in the US. Watch a trailer for the film below: