McGraw and Hill are starring as married couple James and Margaret Dutton in the new "Yellowstone" prequel "1883." They've been filming for months, and the series will debut Dec. 19 on Paramount +.
McGraw told People he's never "had so much fun in my life." Hill says she doesn't want to stop.
But the couple says there have been a few obstacles they had to learn to negotiate on set – like using the restroom while trussed up in period-specific costumes.
"There's just so many layers of clothing," Hill told People. "Sometimes you're successful, and sometimes you're not."
Hill faced another challenge when she and McGraw had to film a bathing scene.
"It was really uncomfortable for me personally because I'm a very shy person in that type of situation," she said. "I obviously feel comfortable with my husband, but this is different. For intimate scenes, I feel like that belongs to us."
However, series creator Taylor Sheridan closed the set the day of the scene, and Hill said, "it turned out to be beautiful."
While McGraw didn't mention the bathing scene, one of the couple's scripted arguments left him a bit shocked.
"We had this scene where she has to slap me," he says. "I was expecting a finger slap, but it was a paw to the jaw. There was 25 years of pent-up aggression going on! When you see it on screen, you realize it was a genuine hit."