Sebastian Stan Calls Mimicking Donald Trump’s Mouth Movements for The Apprentice ‘Tricky’ (Exclusive).Linh

For Sebastian Stan, playing Donald Trump in The Apprentice had some upsides since the former U.S. president is so well-known.

“I think that, fortunately, when you’re playing real people, there’s a lot of things out there that you can watch and grab onto and try to,” Stan tells PEOPLE.

One of those things was the way Trump, the 2024 Republican nominee for president, moves his mouth when he speaks.

“That was a tricky one with him,” says Stan, 42, noting that it’s a big part of impressions and caricatures of Trump that he wanted to avoid. “So it was sort of fine-tuning and trying to not ignore it entirely, but also not overdo it.”

Stan also notes that it has become more prominent since the 1970s and ’80s, the time frame covered in the film, a fictionalized look at scheming attorney Roy Cohn’s influence on young real-estate developer Trump.

“It kind of evolves over time. I mean, if you look at him back, [it] was still there but not as pronounced,” he says.

Costar Jeremy Strong, who plays Cohn, says he and Stan “both did pretty extensive research” on the men they portrayed.

“You kind of have to give yourself a master’s degree in whatever subject and person you’re playing, so it was an exhaustive process of learning and absorbing and internalizing everything you possibly can from every inch of the source material and books,” he says.

Strong adds that he and Stan each wanted to go beyond a “cosmetic impersonation.”

“Our interest was trying to understand these people humanistically on a deep level, understand their behavior, their motivations, and then render that in a really exact way,” he says.“We have this way of thinking that people are larger than life, but there are large personas in life, and these are two of them,” Strong continues. “So you kind of have to commit to that. And I think if you commit to that from the base of your spine and the soles of your feet, it can have that size, but also be human.”

Maria Bakalova, the Oscar-nominated star of Borat Subsequent Moviefilm, previously told PEOPLE she did extensive research in order to play Trump’s first wife, Ivana.

“I did a lot of prepping. I watched everything that was out there. I watched her clips. I watched her appearances, late-night shows, early mornings,” she said.

The Apprentice is in theaters now.