Hi guys. I just stop by too say, I just got into playing double stops, power chords, and octaves with my thumb rather than using the guitar pick. For some strange reason, when you play double stops, power chords, and octaves with your thumb, the sound is more softer, mellow, gentle, pleasant, and easy too listen to. But on the other end, when your playing double stops, power chords, and octaves with the guitar pick, the sound is more harsh, rigid, and also hard too listen to. And guys I kid you not, playing the minor blues scale as octaves only with your thumb, sound so much more pleasant and makes you sound like... I kid you not a real professional!
As of right now, I even got into started playing scales with my thumb rather than my guitar pick. Why....? Playing scales with your thumb has a soothing effect on me and should have a soothing effect on your other musicians as well. One thing I will say is that playing octaves with your thumb, (I kid you not) makes you sound more as though you have a jazz box guitar (because of the sound it produces) when your actually just playing on a Stratocaster. How weird is that.
And so I strongly urge you too get started using your thumb, when playing double stops, power chords, and even octaves. Cheers! ^_^