tld, Just put the garden hose in the park's sewer input. Place it so it won't pop out once the stuff starts flowing.
For over 20 years, we had a trailer permanently parked is a membership campground with no sewer. When the black tank was full, I used a macerator pump to get the contents from the tank to the 32 gallon prtable tank that was then pulled to the dump station.
Being as the trailer was old, the pump was powered by an extra 12 volt battery. The short "stinky slink" hose was hooked to a clear extension with a sprayer like this:
...so the black water tank could be given a good douche after emptying. The macerator does a nice job of pumping 50 or more feet through a 3/4 inch, or larger, garden hose. Be sure that absolutely nothing but pee, poop and TP goes into your toilet!
You would be surprised what one friggin Q-tip can do to make your macerator inoperable as you are part way emptying the tank.
Don't ask how I know.