TORONTO -- Academy Award-nominated actor John Hawkes says he didn't know co-star Helen Hunt very well at all before filming their fumbling sex scenes in "The Sessions" -- and that was probably a good thing.

"(They) called for an awkwardness and for an unease between the characters, so we kind of had that already," Hawkes said at last month's Toronto International Film Festival.

"I think we were both wondering what would happen.... We didn't rehearse a great deal, turned on the camera and away we went."

The film -- which opens Friday in Toronto -- is based on the life of the late poet and journalist Mark O'Brien (Hawkes), who was paralyzed from the neck down and largely confined to an iron lung after a childhood bout with polio.

When the Berkeley resident decided in his 30s that he wanted to lose his virginity, he enlisted sex therapist Cheryl Cohen Greene (Hunt) for "physical intimacy sessions" and later wrote about the experience.

Director Ben Lewin shot the big-screen version of those "sessions" chronologically, notes Hawkes, 53.

"Those first moments of us meeting and her trying to remove my shirt and all those things, those are really happening in real time," he said. "We didn't talk about it or anything else."

Hawkes, whose long list of acting credits includes TV's "Deadwood" and his Oscar-nominated turn in 2010's "Winter's Bone," says he closely studied a 1996 documentary on O'Brien by filmmaker Jessica Yu.

"That's really where I got the voice and a lot of ideas. I really studied that," he said of the Academy Award-winning doc, entitled "Breathing Lessons: The Life and Work of Mark O'Brien."

Hawkes is virtually unrecognizable in "The Sessions," his breathing laboured and his voice strangled. To convey O'Brien's twisted spine, the actor rigged up a soccer ball-sized piece of firm foam rubber to lay on during filming and was still feeling back pain at the festival.

"It was harder to breathe, it was harder to speak," he said of the unusual prop, adding that the pain was nothing compared to what the physically challenged face on a daily basis.

His exhaustive preparation for the role is already paying dividends. "The Sessions" won two prizes earlier this year at the Sundance film festival, and also received a rapturous reception in Toronto.

Hawkes and Hunt, meanwhile, are already being touted as award season favourites.

Hawkes says it's always difficult to tell during filming whether a project will be successful, but that he had great faith in the filmmakers, including Lewin -- himself a polio survivor.

"You can never tell, but I loved the script so much and really fell for Ben Lewin and his wife (producer) Judi Levine, they're just such great people."

Although Hawkes initially fretted that the O'Brien role should be played by a disabled actor, Lewin said at the festival that he sought out such a performer but simply couldn't find one.

"The very first thing I thought of is: 'If only I could find a real person to do this,"' said Lewin.

"Now, at a certain point it becomes slightly farcical -- a real person, you mean someone who needs a machine to help them breathe? You know you can't subject a person as fragile as that to the ordeal of making a film."

He continued: "I mean no one ever gave me a break as a writer or director saying: 'He's disabled, he needs the money.' Nor was I going to do the same for anyone."

Once Hawkes got past that hurdle, he focused on mining the humour in the film.

"Ben said something really interesting, he said: 'I don't want Mark to be a saint, I want him to be a real human being, which is sometimes ... a real jerk."'

O'Brien's wry sense of humour permeates the film, often breaking the tension of the "sessions." After working with Cohen Greene, the real-life O'Brien -- who died in 1999 at age 49 -- went on to have a longtime romantic partner. Lewin said her input was crucial to the film.

"The fact that I had Susan Fernbach, his real girlfriend, available to me as a friend and a kind of soulmate and a window into who he was really helped me develop his voice," said Lewin.

Hawkes, meanwhile, seems to have developed an uncanny knack for choosing interesting roles. The actor says his strategy is a simple one.

"I've never been interested in trying to find one thing that I was good at as an actor and just repeating it over and over," he said.

"For me it's just trying to find a great story and a great part in that story and really capable storytellers."

"The Sessions" is due to open in other Canadian cities in the coming weeks.