Driving the Challenger or the Big Boy is completely different. The Big Boy has a total weight of 500 tons while the Challenger weights about 350 tons. Stoking these giants is not an manual issue any more because the large fire box is just too large to shovel. However a transportation system in the fire box will provide coal on every spot on the fire grate a well.
In simulation just stoke these engines as normal, but keep in mind the mechanical stoking system these engines has.
Keep up the water level not decreasing 96% water level. You have to use the injector almost permanently. The US style injector is rather different and uses a lever to open up the water pump. This lever provides either power and either water in one motion and pumps this water into the boiler.
To stop these giants is even more different and difficult a well.
Cut off the regulator until 20%.
Position the reverser slowly backwards in reverse and open up the regulator slowly.
The cylinder now will use the steam power to slow down the train. In some sort of way it acts like a regeneration brake on electric trains. However steam is not regenerated, but rather used as steam brake but direct on the cylinder and pistons. Steam is the main power to slow down directly.
When the speed has decreased and reached the desired speed or less, position the reverser in the middle
Set the regulator at about 10% and continue braking using the normal brake system.