Watch the Double Stop Junction online guitar lesson by Matthieu Brandt from Modern Mountain Banjo: Clawhammer & Up-Picking
As the name implies, this song is full of double stops and triple stops, but it's main feature is the intense use of double thumbing. When you play this technique up tempo, you can get a very full sound and some great syncopated rhythms that you won't get out of simple "bum ditty" or Pete Seeger up picking.
Your options to play syncopated rhythmic patterns will increase, but drop thumbing at higher tempos is of course a bit more challenging. Most of the time the pedal string will be muffled by keeping your right hand close to the skin and strings. Sometimes you'll also have to break up your right hand double thumbing motion, especially if you want to use the pedal string in a melodic way.