The Oscar buzz surrounding Gary Oldman’s turn as Winston Churchill has been deafening since “Darkest Hour” hit the festival circuit last August, and he’s already racked up the lion’s share of this season’s accolades.

But when Oldman first met with producers and director Joe Wright for the Focus Features movie, he was open about his concerns. “I said to them, ‘We’re not talking about the elephant in the room, which is that I don’t look anything like Churchill,’” Oldman recalls. “I don’t know how this is going to be done, but if there’s one man who has even a remote chance of pulling this off, that’s Kazuhiro Tsuji.”

Makeup artist Tsuji had established himself as something of a miracle worker, having transformed Jim Carrey into the Grinch and helped Joseph Gordon-Levitt resemble a young Bruce Willis in “Looper.” There was only one problem: Tsuji had been retired from the business for several years, choosing to focus on his work as a sculptor — primarily oversize, realistic renditions of famous faces such as Abraham Lincoln, artist Frida Kahlo and his mentor, makeup legend Dick Smith.

Oldman and Tsuji had never made a film together, but they came close: They met when Tsuji did a face cast of the actor for Tim Burton’s 2001 “Planet of the Apes”; the role was ultimately played by Tim Roth. Still, Oldman remained a fan of Tsuji’s work as both a makeup artist and a sculptor, and sent the artist a plea via email. “He told me he would do this film if I said yes,” says Tsuji, adding with a laugh, “It wasn’t threatening; it was very nice.”

Nevertheless, Tsuji was hesitant. He had not enjoyed his time in the film business; he notes that after “The Grinch,” he had gone into therapy. “I had made a promise to myself to leave the business, and I felt like I would be going back on that promise,” he admits. “At the same time, I’d never really had the opportunity to work on a great movie with a great actor in a serious story.” Ultimately, he says, “It was kind of a dream project, so I had to do it.”

Asked if he was ever worried he might not be able to turn Oldman into Churchill, Tsuji doesn’t hesitate. “Yes, of course,” he allows. Six months of makeuptesting ensued. “Likeness makeup is almost impossible to pull off because everybody looks different,” Tsuji explains. “If the two people have proportions that are close, it’s easier. But these two are totally different. So I had to figure out the best balance to make him look like Churchill, but not [like he’s] wearing a mask.”

Meticulous detail was paid to the complexion, with Tsuji painting every mark and blotch by hand. The wig was made from hair not just from adults but from babies, to ensure the thin, wispy look. Oldman would ultimately spend four hours daily in the makeup chair, where David Malinowski and Lucy Sibbick oversaw the application. Removing the prosthetics took an hour at the end of the day.

The final product is so flawless, Oldman says, that he’s had to convince people it actually is makeup and he didn’t pack on pounds for the part. Tsuji has received his third Academy Award nomination, and Oldman cautions Tsuji that his retirement might not last long: “I’ve already spoken to some people who want to give you a call,” he says.