We bought one of these (it's actually 2 parts)
http://www.campingworld.com/browse/p...=2399&src=SRQB
and think it works pretty well.
I have read that you shouldn't leave your grey water tank valve open because (1) sewer gases can make their way into your plumbing system and (2) you need some grey water in the holding tank in order to wash out the hose when you empty your toilet black water.
We still have one person hold the end (or put their foot on it) that goes into the campground sewer outlet when we dump because there's always the chance that the hose will "kick" when you open the valve and cause the connection to become undone. We always double check the hose connection on the TM outlet before we pull the drains (this extra step was implemented after one bad experience
).
Have fun with your TM!