I have the auto tank cleaner in our new Jayco, but that doesn't always get ALL the "Crud" out. We also keep a 5 gal pail and fill that with the shower and dump that all at once a few times and that seems to get the stuck stuff out of the tank. Those big gushers of water really move the stuff. We have a clear extension pipe before the sewer hose so you can tell when it's so called clean.
Hope this helps you as much as it's helped us.
2016 Pinnacle 36REQS
2014 Ford F-350 6.7 4x4 CC LB Dually
Mike & Chelle, My kids when they decide to go with us.