When in doubt it often works best to follow the manufacturer's operation manual. You can download the Atwood water heater manual here:
https://www.gulfstreamcoach.com/medi...lon-Manual.pdf
In that manual is the "manufacturer's procedure for flushing and sanitizing the tank"... It is not the same as the Suburban water heater procedure, because the storage tanks are made of different materials. The Atwood tank is aluminum alloy and requires no anode rod while the Suburban tank is porcelain coated steel and does require an anode rod. It makes sense that the two types of tanks would react differently to some chemicals....
So, here's the "cut and paste" from the Atwood manual:
FLUSHING YOUR WATER HEATER TO REMOVE
THE ROTTEN EGG ODOR
1. Turn off your main water supply. Drain you water
heater tank. Reinstall drain plug. Remove the
pressure-temperature relief valve. With a funnel
use 4 parts white vinegar to two parts water. (In a
6 gallon tank that would be 4 gallons vinegar to 2
gallons water).
2. Cycle the water heater, letting it run under normal
operation 4-5 times. At no time do you remove the
vinegar from the tank Once this has been
completed, remove the drain plug and drain the
water heater.
3. After thoroughly draining the tank, to remove the
sediment, flush the water heater.
If you elect to use air pressure, it may be applied
either through the inlet or outlet on the rear of the
tank or applied through the pressure-temperature
relief valve. Remove the pressure-temperature
relief valve and insert your air pressure through
the pressure-temperature relief valve coupling. In
either case, with the drain valve open, the air
pressure will force the remaining water out of the
unit.
If air pressure is unavailable, your unit can be
flushed with fresh water. Fresh water should be
pumped into the tank either with the onboard
pump or external water pressure. External
pressure may be hosed into the unit either
through the inlet or outlet found on the rear of the
tank or the pressure-temperature relief valve
coupling located on the front of the unit.
Continue this flushing process for approximately
five minutes allowing ample time for the fresh
water to agitate the stagnant water on the
bottom of the tank and forcing the deposits
through the drain opening.
4. Upon completion of the steps above, replace the
drain plug and the pressure-temperature relief
valve.
5. Refill tank with fresh water that contains no
sulphur.
The Atwood water heater is designed for use in a
Recreation Vehicle. If you use your vehicle frequently
or for long periods of time, flushing the water heater
several times a year will prolong the life of the storage
tank.
And a "cut and paste" of that part of the manual.