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...
When we had a TT with a full bathroom, we only used our tote for grey water, never black - yuk! We used the campground facilities during the day, and our toilet at night, so we could go a week before filling up the black tank. Get a tote that you can hook up to the hitch ball and drag to the dump station - much easier this way.