Hey Pat, Welcome to the forum. Lots of great people with good ideas and experience.
I agree with all Tim said .............Except .............. the "drying out" part.
When you "dry out " the black tank, any TP or Solids residue will "cake"
in the tank. They ALWAYS seem to find the sensors. Keep them wet!!
I always travel with 5gals or so in each tank, add your chems, and let it
Slosh and work for you.
Best regards, Clyde