The National Geographic Channel film based on Bill O'Reilly's best-selling book of the same name is to premiere Sunday.
"I worked forever, oh my gosh," Lowe said Friday on "The Ellen DeGeneres Show."
"He's such an icon. We all know how he looked, how he moved, what he sounded like. And as an actor, you have to get that right. But then you have to do all the other things we do for any other role, which is making him a recognizable human being," Lowe said. "It's double the work. I just spent hours and hours and hours listening to the voice and working on it because it has to be there."
The movie is to premiere Sunday night.