Learning to hold a brush like Britain’s most revered landscape artist could be considered the easiest way to embody the role of J.M.W. Turner. But for Timothy Spall, who stars as the titular “Mr. Turner,” perfecting the artist’s signature grip was merely the first step in his quest to paint like a master.

“The job really was to get as much knowledge about the practicalities of the painter, try and understand what he was doing,” Spall says. “Basically, we were trying to make it look like I was familiar with a brush, like it was something that grew organically out of my whole being.”

The actor trained with watercolorist Tim Wright off and on for two years before he began shooting Mike Leigh’s look at the last 25 years of Turner’s life and prolific career. After a rigorous examination of the basics, Spall punctuated his abbreviated art degree in a grand way.

“It culminated in me painting a full-scale copy of one of Turner’s masterpieces, which I have on my wall at home in a frame similar to the one that’s in the National Gallery,” he says. “I look at it in the morning and I think, ‘How the bloody hell did I do that?’ ”

Yu Tsai for Variety

While Spall spent an extraordinary amount of time absorbing the details of his subject, he’s one of many who find that the best way to portray a character convincingly is through meticulous research and training. Amy Adams and Christoph Waltz also learned to paint for “Big Eyes”; Channing Tatum learned to wrestle for “Foxcatcher”; Matthew McConaughey and Anne Hathaway interviewed NASA astronauts for “Interstellar”; and Eddie Redmayne used months of research to transform himself physically into Stephen Hawking for “The Theory of Everything.”

It’s all in the interest of authenticity. Just as Spall wasn’t interested in mimicking a painter, Miles Teller wanted to look and sound technically correct as a jazz drummer in “Whiplash”— particularly because he played all the songs in the film. Though Teller had been in bands since high school — something director Damien Chazelle didn’t know when he cast the actor — he quickly realized that knowing how to play in a rock band just didn’t cut it in the jazz world.

“It’s all completely different, even the time signatures that jazz plays in,” says Teller, who trained with co-star Nate Lang for about three weeks before shooting. “The way (jazz drummers) sit — it’s a bit of a hunch. It seems like they’re sitting right over the snare drum, so that was different for me. The way that you hold the stick affects the way that you hit the drum. They call it painting the snare drum because it’s more of a flick of the wrist than it is a hitting motion.”

Though Teller was able to transform a skill he already had for “Whiplash,” “Into the Woods” star Emily Blunt says she had not had any formal vocal training before taking on the role of the Baker’s Wife in Stephen Sondheim’s musical. However, rather than looking for perfection, she was more concerned with conveying the meaning and feelings of the lyrics.

“I went into pretty ardent vocal training with Eric Vetro, who really raised my confidence,” she says. “It was exciting working with Sondheim’s music, which is so emotionally complex that you don’t have to make it sound pretty and glorious. You have to make sense of what he’s trying to say with his songs and all the nuances. In a way, that’s a relief because then I’m doing something that I know more about.”

For Jake Gyllenhaal, getting into the mind of a freelance cameraman in “Nightcrawler” built on the knowledge he gleaned from LAPD officers when he prepared for 2012’s “End of Watch.”

Yu Tsai for Variety

“I had spent five months on the streets of Southeast L.A. with police officers three or four nights a week living the same schedule but with people who are actually supposed to be at the scene,” Gyllenhaal says. “When it came time to do this movie, I had no idea that fate would put me on the other side of the line. But I had a perspective on those scenes, a very intimate one, one that changed my life. To be observing it and trying to watch guys who are feeding off of it in a way was an interesting process.”

Truth was also important to Hilary Swank in playing a frontierswoman in Tommy Lee Jones’ “The Homesman.” For the role, she had to hone her horse-riding skills, learn to steer a plow and drive mules pulling a wagon. She had about two weeks to learn from four different experts, and she spent most of her time between scenes working on her riding.

“I was at best a recreational horseback rider. So I had to learn to ride a horse and make it look real,” Swank says. “Learning anything to make it look convincing and have it in your bones takes time. By the way, getting on a horse with a 25-pound dress is a stunt in itself.”

Swank says learning to work the land like a Nebraska Territory settler was the ideal way to get to know her character.

“I love the physicality of playing characters and understanding them from the inside out. It’s where a lot of my passion lies,” she says.

Whether it’s intense research or learning a new skill, the mental and physical preparation for a role can be just as rewarding as a series of stellar rehearsals. “I really don’t like to be rushed,” Blunt says about her prep work. “I like to have time to think and ponder and go over it. It’s always about finding an in with the people that you play.”

“It’s absolutely essential to me,” Gyllenhaal concludes. “I believe very deeply in the unconscious. To get to that place in yourself requires great preparation, and freedom is on the other side of discipline. Spending that time is my favorite part of working.”