I just use a back flush gadget like this** or the back flusher on the macerator, depending on how my sewer hook is at a campground. I've found the macerator version works much better then the built in arrangement or the Valterra/CAMCO
**
http://www.valterra.com/product/flus...h-valve-boxed/
I also made up a flusher to shove down the toilet from an old hose cut down to a manageable length with a l90 degree awn sprinkler head clamped on the end. That one works well too.
If it's a straight shot, no angle to the holding tank, both Valterra and CAMCO make a wand to shove down the tank. Unforunately our HC has a 45* tank run, which is why I made the one noted above