My version sounds a little different than the movie version (O Brother Where Art Thou) but they are fairly close. The timing is approximate. Be sure to tune your guitar in crossnote tuning. This is a tuning that I’ve heard was fairly popular with the old-time bluesmen but this is the only song I know in crossnote tuning (DADFAD). If you’re familiar with open D tuning, the only difference here is that the 3rd string is tuned down to F instead of F#, which results in an open D minor (Dm) chord.
Here’s the tablature: