I don't know anything about "Tank Techs RX" or any other such product.
I'm assuming you want to clean out the tank due to a problem with the sensor. If that's the problem, fill about half full with warm water and some dishwashing soap, and pull your rig around several turns as well as several stop and go cycles. That might clean the sensor.
The other potential problem has to do with leaving the drain valve open while connected to the sewer system at a campground. Doing that allows a build up of tissue and solid material called a "pyramid". Dissolving a pile of debris requires leaving the tank nearly full for several days and then dumping. Obviously, one doesn't want to open the drain valve until the tank is nearly full, or you are leaving the campground.