Alan, haven't brewed this yet but the yeast will be Wyeast 1007 German ale yeast. From what I can find on the subject of dusseldorf alts, they tend to be brewed cool for ale, and layered as if it's a lager (cold), but I can't be sure that's what JZ's instruction mean in BCS. He just says be sure to lager 4 weeks before bottling
Here's a silly question, but may help...
...what yeast did you use?
There should be enough yeast in suspension if either ale or lager yeast, but I wouldn't do a transfer to another vessel, just let it rest for a while at 50*F. By definition lager means "to rest". Most turn of the century brewing concerns used caves just above freezing to do this. Charley P documents lagering at warmer temps with satisfactory results in his books, its just about letting the lil beasties do their thing over time.