Try the hose method but I found the best way was a suggestion by mcfrmall, to rinse the grey and black water tanks and the p traps by pouring a 5 gallon pail of water down the sinks and toilet. In the black tank the volume of water dislodges most solids. I used my tank flushing system until it ran clear. When I poured the water from a 5 gallon pail it took 7 of them, one at a time, before it ran clear demonstrating the inefficiency of the tank rinse. Search the forum and you will find the threads.
Married To The Navigator
2005 Red GMC Duramax 4X4 HD Crew Cab
4" Magnaflow, Banks Air Intake
Firestone Ride Rite Air Springs