I've heard about using the blue tote for dumping so you don't have to move the rig. When the tote is not as large as the tanks you are dumping from do you just have to wing it and hope you shut it do...
If you're just draining grey waste use one of these and a short garden hose: It drains slow enough you can close the tank valve before it overflows. I use it when we're out in the desert and have no access to a dump station.