In our HTT we added a Tornado and it did a great job....you could certainly see the results on the second dumping. It does not actually fill the tank, but has a sprayer that spins and rinses. The TT has a built in flusher and while we don't use it every time, maybe every 4 or 5 trips or if we know it'll be a while before we're out again. Invest in a clear fitting and you can see what's what. We have used Odorlos for several years and no odors, or clogs, so assume it's doing it's job. Never, never, never leave the tank completely dry. Anything that might remain will be concrete and a major job to clear. When DH is finished with his part of the dumping, I add a dose of Odorlos and about 4 or 5 gallons of water. We rarely carry much in any of our tanks, because of the additional weight, but that 4 or 5 gallons is a must, and it'll slosh around on the drive home and help rinse the tank. The sensors are so unreliable that it's almost a waste of time to check them.
Especially in CA with your water problems, suggest you check into a small dishpan to wash and maybe even one to rinse dishes. When done, instead of dumping in the grey tank, add the water to the black. You'll have more volume and it will help the dumping process. Water is crucial with the black. Not enough water = big problems.