The black and grey tank flush feature is great! The only problem is when a dump station does not have a water hose or the water hose does not have a coupling at the end. Then there is no way to hook-up for flushing.
Rather than dig out my regular hose, I use a 10 foot section of flat hose with couplers on the ends. This makes things simpler as you can see in this photo.
When done dumping, just connect the ends of the flat hose, loop it over the macerator hose-hooks and secure with elastic cord. As you see here.