black water tank -- I see toilet paper

My black tank is long and shallow and is extremely difficult to get it completely dumped. I have a black tank flusher built in but unless I close the tank and let if fill about half way a couple times from the tank flusher it won't come clean. You might try letting it fill for a while. Just don't get distracted or you can flood your trailer! Also mine has to be pretty level to dump clean. Fortunately I have a dump at home and can take my time to do it right if someone is behind me at the campground.