Pick apart the parts to Black Water! Having seen this played in about 15 concerts since the 70s, the second return on the riff (where you play the double stops) is an eighth note pattern on string 5 and 4 and 5: 5 - 5 6 7 4 - 5 4 5 - 5 7 If you split the guitar lines between two guitars, your double stops add some meat in there!