Using the kegland T piece you can dump into the first ( I use a small pet bottle 250ml ) and then Blow off tube from the other port into the under water valve in the growler. No pressure on the system this way for good expression and really easy top harvest of yeast.
I have that tee, as well as a 2nd carb cap. What a FANTASTIC idea!
I'm gonna try this in-line between a ferm-keg and my starSan keg when I purge it for later use!