How I flush my black tanks depends on whether it's a final clean out at the end of a trip or just a mid-trip empty. If I'm in the middle of a trip and just emptying it because it's full, I'll run the rinse while it empties and leave it on until the water runs clear.
If it's my final empty at the end of a trip, I'll empty the tank, close the gate valve and use the black tank rinse to fill the tank with water. Once full, I'll empty it again. I'll repeat this process until the water runs clean. Sometimes It takes 2 or 3 fills before it's clean. I will then dump my grey tank to rinse out the sewer hose. Again, I only do this extra rinsing if I'm done with the toilet until the next trip.
2016 Coachmen Freedom Express Liberty Edition 310BHDS
2015 Toyota Tundra 5.7L V8 with towing package
Husky weight distribution hitch with sway control