Dumping at Campgrounds and Flushing Black Water Tank Too

I try to always flush the black. Only time I don't is if I can't hook up the black tank hose. Some dump sites have no hose connections for rinsing. I can get my black hose connected while the black is draining. Then leave it on while the grey is draining. Only takes a minute to put the black hose away. If it looks like for some reason it will be a hassle I will pass. If I had to refill the black tank to flush again and there was a line then NO I wouldn't do it.