From my understanding, the D&RGW most often used a water hose to empty the pans. Presently on the C&TS, we use compressed air which is effective but messy. You'll note the visible fly ash clung to the locomotives in the vicinity around the firebox as a result of this method. Needless to say, it's good practice to turn off the air pump while blowing out the pan or the air cleaner will become plugged immediately.
I have been successful using a water hose in the absence of compressed air; however, one must be careful not to splash water up into the grates and fire bed.
Dylan Hutson
Ex-Cumbres & Toltec Scenic
Mechanical Dept.