Rid X would be a waste for me also. RVs have holding tanks, and I feel that Rid X would not work fast enough to do anything between dumps, but if it works for you, go for it!! I do put Rid X in my septic at home, it is good stuff.
When I back fill I use a clear bayonet section with a water hose fitting, that is attached to an extra gate valve. I close the valve on the fitting and water is forced back up into the tank. I watch my monitor panel and when it gets close to full, I open the extra valve. After you do this a few times the tank is clean and there is never an odor.
If your monitor panel never shows empty, like Nash says drive with some water in the tank and it will probably clear the sensors up.