It's never easy getting naked for the cameras, even if you've stripped down onscreen before.
"She coached me through my first nude scene," Evan told E! News last night at the series' NYC premiere. "I mean, she's done it all. She was literally next to the camera going [thumbs-up]."
How exactly did Kate help her younger costar through it?
"Helping her to fully acknowledge the weight of that within the story. And also just talking to her about how to find a level of confidence," explained Kate, who plays Evan's mother in the movie.
It also helps to keep the spectators to a minimum.
"You keep the room as empty as possible and just kind of being there for her, really, and letting her know there was someone to hold her hand and throw a robe over her at the right moment...made her feel better," Kate added.
But the Oscar winner did convince Evan to cover up a bit.
"I looked at Kate and she was like, 'You've got to do it. Trust me, it's so brave. Put a merkin on and you'll be fine," Evan told Fancast.com.
(A merkin, by the way, is a wig fitted for the pubic area. Apparently people didn't get Brazilians in the '30s, when the movie is set.)
And while Kate's dropped trou tons of times herself, she says it's still scary.
"It is really strange, nudity," the hot mom said. "I know I've done it many, many times now, but you never really get used to it. You don't!"
—Reporting by Vanessa McDonald