I have a factory black tank flush system but I use a clear adapter (without hose attachment) so that I can SEE how well the stuff flows out and when rinse clears up during flush.
I leave it attached to end of drain line all the time.......mainly because it seals real tight and is hard to get off.
When we have a FHU site I set up everything...water/electric and sewer.
Dump as necessary and then tear down on day we leave.
Only time anything is visible is when dumping and if folks want to stand around and watch that's there business.