Jerry.....On the Monaco coaches, they installed a sprayer on the passenger side of the coach at the top of the black tank. The sprayer has several small holes in it so that it has a shower affect. When your black tank gets above 3/4, the waste sloshes up into the sprayer and dries hard.
Like I said, the sprayer is on top of the tank and has a hose line running to it that is hose clamped on. You can remove the hose, unscrew the sprayer and clean out the sprayer holes. The problem is, it will do it again. I just left the sprayer in place, removed the hose and used an 1/8" drill bit and drilled down into the sprayer several times. This enlarges the holes and will prevent clogging. It will no longer have a shower affect, but all you really want is a flood of water at the opposite end of the drain.
Don & Mary
2019 Newmar Dutch Star 4018 - All Electric
2019 Ford Raptor Crew Cab