The former "That '70s Show" star admits he had been stumbling over some of the words as he prepared for his audition, so he decided to be upfront with Lee and explain the trouble he was having with the script - before he even got the part.
"I had to go in and read for (Lee), because... I just hadn't played any roles like that, and the night before, I was preparing for it... and I couldn't say some of the words that were in the script," Grace recalled on U.S. talk show "The View".
"The next day I went in and I had this little speech prepared for him. I said, 'You know, I'm really having trouble with this' - and this shows what a great director he is, he immediately went to work making me feel so comfortable, that I could then give a performance that would allow him to give me the role."
Grace continued to experience how accommodating Lee was on set as they worked together on the biographical 2018 movie.
"A lot of it was like that on set too, him coaching me through it...," he shared. "I know he still teaches, he's kind of a teacher like that on set too, and a coach, and just an amazing human to work with."
And Grace insists he only ever considered taking on the "heavy subject matter" because he wanted to work with Lee.
"The research for that movie was just devastating and not something I wanted to do, but I thought I'd never want to play this role if not for the opportunity to do it with Spike," he added.