The problem you mention is a common one with a lot of SOB trailer that have the bathroom on the curb side of the trailer, never enough water to move the masses. If your Airstream has the toilet on the street side, close to the dump valve and you are using a full tank of water per flush you should not have a problem. Depends on how much time and effert you want to put in.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles