After reading Ian C.'s post about the proper method of agitation by tray-rocking, I'm going to retract my rather hasty condemnation of that method. It was occasioned by the practice of so many of just wiggling the tray around a bit and then complaining of uneven development. Certainly, any agitation that uniformly replaces the exhausted developer at the surface of the film will work well. Developing time will be unique to the agitation method.
Tray rocking, however, seems to work with just one sheet (plate) at a time. For those of us who develop larger batches, the shuffling method has become fairly standard.