So this is probably the easiest song ever.  At least the stringed rhythm part.  Played 
a mandolin, I'm pretty sure (it sounds like the noise my mandolin spits out), but still 
not bad with a plain old acoustic.

Dm Gm

In between the chord change, strum the strings open once so that it sounds like what he 
doing.  Play each chord for two measures, listen for the rhythm, and  just rinse and repeat.