Stalling on the Grade

I have often wondered what it is like when an engine stalls on the grade. I assume the engineer and fireman are aware of a heavy pull ahead and do all they can to assure that the fire is hot, there is plenty of steam, and the engine is operating at full power.

But when the speed gets down to a crawl, what happens in the cab? What levers a pulled and for what purpose? What happens when the train actually stops? Do the engine wheels spin? If not, what damage might occur to the cylinders if there is no motion, yet steam pressure is at the highest point? Could there be damage to the internal components of the engine or to the valve gear?

With regard to engines, are the strategies that the engineer and fireman use when faced with stalling different? For example, is there a difference between operating a 480 series engine and a 490 series on the grade when pulling a heavy train and faced with a stall?

If there are any present or former engineers and fireman out there, I am sure they can shed some light on what must be one of the most dramatic events in operating a steam engine.