Mine works fine also but I do a little more than just hooking up and flushing. I will do the normal flush for about 5 minutes. Then I close the black tank and fill it with water. Just be careful and have a spotter so not to overflow the tank as well as checking your panel to check it's capacity. Once filled, I open the valve and let it flush again. If possible, it's beneficial to take a little drive to slosh the water around but not necessary. You'd be surprised how much more "black waste" comes out. If you feel you need to, you can repeat this process. I know everyone has their own system but this is mine and it seems to work pretty well.
2013 Jayco Eagle 328 RLTS
2012 Ford F250 6.2L 4x4 CCSB W/Air Lift air bags
2002 Coleman Bayside Elite (traded)
Me, Momma and Charles (RIP buddy)
And introducing Sofie!! ;)