I keep a length of hose for grey water draining. I cut off the other end so it cannot be used as a water supply hose.
When we dry camp I have one of the sewer caps with a hose bib on it. I hook up that hose and run it to a bush or grassy spot and open up the grey tank valve.
If in a full hookup site you can run that hose to the sewer connection. They do make plug things for it or you can just make one yourself out of a 4" PVC pipe cap.
2017 Eagle HT 29.5BHOK (sold)
2017 Ford Powerstroke 6.7, Crew, 4x4 (sold)
2018 Toyota Highlander
Maggie, Old English Sheepdog