Evidently so, according to The New York Times, which semi-interviews and profiles him in advance of the Coen Brother’s True Grit opening.
And if you haven’t read the original novel it’s well worth doing so. Not my favorite western (or even my favorite western made into a John Wayne movie, as Glenden Swarthout’s The Shootist edges it in both respects), but certainly in the top five. Of course, I only recently started reading Lonesome Dove, so I’m far from an expert…