Paul had a great time working on the song for Jerry's record.
"And then I played it for Paul, and he said “Oh, man — I want to be on that.” So we did it with him anyway. [Laughs] He did a ton of stuff that’s just mixed deep in there. Rhythm guitar, tons of stuff that’s on the backbeat against my solo, big bells — some really high harmony vocals. He had the greatest time, he spent the whole day going until we made him quit. It was beautiful, and it all just kind of fell together like that."
From American Songwriter, Hard Travelin’: A Q&A With Jerry Douglas, page 2.