IF you have access to grey tank you can add a tank flush system.
I prefer 'simple'......
A clear adapter goes on end of drain line and then sewer hose goes on.
Open drain valves and you have a visual of what is flowing, how well it is flowing and when it stops flowing.
I haven't looked at the monitors in years...don't care what they indicate I know tanks are empty.
Don't care if the tanks are squeaky clean....just sufficiently rinsed....gonna dirty them up immediately.
Don't worry about 'smells' as all seals, traps etc. work
Don't worry about when to dump them either.
Toilet 'burps', shower sink start to drain slower...time to dump/rinse.
Takes about a week between dumps.