Proper procedure for black tank rinse/sanitize

After I dump the black tank, I leave the valve open and flush for awhile. Usually there's still solid material, including TP, hanging up at the valve gate. If I close the valve at the end of the first dump, some of that TP tends to get stuck in the valve seat preventing full closure the next time. While flushing, when the water looks mostly clear, then I'll close the valve and do partial fills of the tank to get more solids out.