get a stick about 3 feet long, hold the toilet valve open and knock that sucker down, then properly dispose of the stick, or clean it up for the next time, drop some enzimes in the tank with a few gallons of water.
after you dump or try to, put 10 gallons of hot water (very warm at least) with a cup of liquid laundry soap (or 2) and drive for an hour, make sure you do some hard turns and curves, some bumps and roads that cause vibration. then go dump, your tank will be cleaner than new
warm / hot water dissolves and cleans 10 times better than cold water ever will.
I do this at the end of the season and sometimes midway depending on usage, and one good rinse after dumping and the tank only returns clear water with no floaties with further rinses
