Hugh Lovel said he likes human-powered BD prep stirring that is done with a tripod stirrer over a barrell, the kind made by Greg Willis, that they made a real nice vortex. These were in use at Topolos Vineyard in Sonoma County.
Slide #3 and #4 in the RealSlideShow on my "farm home" web page shows the tripod stirring device and the vortex, from the Biodynamic Viticulture Field Day at Topolos Vineyard a few years back when Hugh was teaching with Peter Proctor over at Steiner College. It's a Beautiful Day A RealSlideShow sampler http://www.ipa.net/~steved/audio/ Steve Diver