I also recommend Buhner. He's not coming from a classic occult tradition, but rather what he calls a "vegetalista" tradition. He's not working with (visualized) energy or qi, so I'd think his exercise plays well with JMG's druid traditions - especially because he emphasizes connection with nature, communication through the heart, and deep listening to other species/beings that are part of the world around us.

Funny, Jeff, you asked the reverse question of mine last week (I said I was more familiar with heart-centered ways of knowing, rather than solar-plexus-centered ones and asked for solar plexus reading materials). :D