I found I really started enjoying rangefinder shooting when I had a feel for the aperture range that I liked and didn't have to look too much at the DOF scale. Usually that means about one or two stops from wide open with whatever lens I have, and the fastest shutter speed I can use. Closer to wide open, I think, you get more of a sense of what a rangefinder lens can do--really sharp subject, soft background. Try sticking around f:8 for a while.