I"d just not dump it if it's not full. It's NEVER a good idea to dump a partially filled tank and in those rare occasions when you feel you MUST dump it, fill it with fresh water first THEN dump it. You need LOTS of liquid in the tank to flush solids across the tank to the drain. Leaving those solids inside will eventually cause a clog and/or odors. As for problems in cleaning sensors, I've use the same mothod for some 40 years of RVing. I just dump (quickly) a couplel of 5 gallon buckets of water through the toilet after dumping and it haven't failed me yet.