However, when it comes to his own work, he likes to wing it a little.
That's what he says he did in "War Witch," which is in contention for the best foreign-language film Oscar being handed out in Hollywood on Feb. 24.
"We had written all of the script but then when we started filming, I decided to not show the script to the actors and to work through directed improvisation," he said in an interview with The Canadian Press in advance of the ceremony.
"We shot this film chronologically and I had specific expectations but the actors had a lot of freedom to listen to where their instincts would guide them. What's very eerie, when you look at the film and you read the script, there's a lot of similarities (between them)."
It took him 10 years to write the script.
Yet at the end of that lengthy process, when it was time to film, he would simply describe each scene to the actors, explain what he wanted — and they mainly took it from there.
In one scene, for instance, one of the actors who was a real-life soldier points to a deep scar on his neck from a bullet wound and describes how he got it. The story was true — he'd suffered the wound in real combat.
"War Witch," which is also known by its original French-language title "Rebelle," is the compelling — and often heartbreaking — story of child soldiers in an unidentified African country.
It focuses on Komona, played by Rachel Mwanza, who is taken by rebels at the age of 12 to join their army after they force her to kill her parents.
Mwanza was living on the streets in Kinshasa. She had never acted before being cast in the film yet her performance has drawn widepsread acclaim.
"She had so much courage," said Nguyen, explaining the novice was able to be herself in front of the camera and exhibit a kind of nonchalance free of excessive self-analysis. Nguyen said that's a quality more experienced actors often lose.
"You can't learn that. You have it or you don't and Rachel had that."
"War Witch" is a bit of a rarity because most films about child soldiers are documentaries.
Nguyen agreed that sometimes drama can drive home the impact of such an issue because it puts the audience in the shoes of the subject more than a news report — letting them see things, for example, through the child soldier's eyes.
"There is that strange feeling that by transgressing reality you're being truer to the emotional scope of a child soldier or a character," he said. "Sometimes fiction brings you closer to truth in many ways than trying to be historically accurate."
Despite the explosive topic, Nguyen managed to avoid being preachy.
"Film is able to project grey zones without words, without predefined judgment and just bring reality to the front . . . and let the person watching make their own decision," he said.
Nguyen was originally inspired to do the film by a news story about child soldiers, especially the tale of a nine-year-old Burmese boy who rallied soldiers around him after declaring himself a god.
Besides its scenes of combat, "War Witch" gives a surreal twist to the traditional coming-of-age story as its characters show flashes of being typical teenagers and blossoming first love amid the brutality of the fighting.
Nguyen says he dealt with his own concerns about putting the different layers of reality together, in order to demonstrate that love is no stranger in wartorn countries.
"These quests for idealistic love are still there. They're the same as here and sometimes they're even stronger because that's the last thing that people can hold onto."
Nguyen didn't have to think long when asked about the biggest challenge of filming in the Democratic Republic of Congo, which is still shaky after years of civil war.
"Getting insured," he said with a laugh.
"This was a challenge right from the start."
Logistics and security were no picnic, he explained, because the country is still chaotic.
"Sometimes we watched the film and we were amazed we were able to pull through," he said.
And there were a few close calls.
For example, the crew had to warn the public via the media when scenes called for gunfire so there wouldn't be a panic.
The warnings didn't always work.
Within minutes of one scene where volleys of fake bullets were fired, the crew beheld clouds of dust billowing toward them.
"It turned out to be about 20 military vehicles with grenade launchers on top of them and real soldiers with AK-47s going to annihilate us because they thought we were rebels.
"Our logistics manager stepped in front of the road and said, 'No, no, no. It's the Canadians!'"
The other tricky aspect was directing the improvised nature of the production.
"Everybody was really free so it makes it even more difficult to kind of guide the herd to make this kind of cohesive thing where it's more organic but at the same time it's headed in the right direction," he said.
Nguyen, who heaps praise on his fellow nominees, is excited about going to the Oscars. He even smilingly handed out tickets for a bet on his film in the Loto-Quebec Oscar pool for best foreign-language film.
He also followed a tradition started by previous Canadian foreign-film nominees Denis Villeneuve and Philippe Falardeau and ate a bowl of Lucky Charms cereal the day the nominations were announced.
He said it's still too early to tell what effect the Oscar nomination will have on his career but said people he'd like to work with are open to talking to him about future projects.
He and the crew have rented a big house where they'll stay when they attend the Oscar ceremony and Nguyen compared organizing the trip to planning a wedding.
"You've got a certain number of people you can invite," he said. "Everybody wants to come.
"We'll try to keep it as sane as possible but it's really insane."