The American Idiot singer plays a washed-up punk rocker in Kirk's new film Ordinary World and the moviemaker wanted to make sure his leading man had the skill set to carry the project.
The director admits he didn't have Armstrong in mind when he wrote the movie, but he's glad he and the singer crossed paths.
"I didn't really have an actor in mind when I was writing it," he tells WENN. "I assumed I was going to have an actor who played music rather than a musician who acts. But it worked out in a wonderful way.
"I thought that was a brilliant idea, seeing him in that kind of a role. He was eager to do something. He told me his agent was sending him a lot of material to look over and this was the first thing that caught his interest.
"For the acting part I worked with him for nine months, and I just wanted him fully prepared to just be in the moment and get an honest performance with whoever he was in the scene with."
Billie Joe also impressed his co-star Judy Greer, who heaped praise on the rocker.
"I wanted to work with Billie Joe Armstrong, he's amazing," she recently told Press Association. "I have been a Green Day fan since forever. I thought he was brilliant and it was so fun to watch him and work with him.
"He's a total peach. He is such a normal guy. He loves his sons and his wife and all his dogs and just loves to play music. I thought it was such a good role for him."