We are currently parked in an area at Quartzsite where we have water. elec and a shared dump. Needs a bout 60' of hose. Uphill by a couple feet. Think about it.
OK, dump the black, the force etc pushes it all out to the end, then grey. So, now we have 60' of 4" hose full of grey water. Here is my trick to drain the hose. I have a piece of conduit about 8' long, to that I have attached a C shaped piece of steel, 4" across. Disconnect the hose from the dump, bungee it onto the c bracket. Then lift it to vertical. Now the hose has elevation above the highest point of elevation and it drains.
Rinsing works the same.
Way better than when I first got here and did he worm dancce, holding up a ^ portion.
This isn't something you would need very often, but it sure has come in handy this time.