FACT, RGS 20 will have ash accumulation. Not as much as larger engines but it is there. Mostly towards the rear around the side air holes and rear screen, cutting down the air flow. This ash pile up can also make it easier for hot chunks fall out and set leaves on fire between the rails.
Best way to remove this is an old school tool called and ash pan hoe. Bit of 3/8 (give or take) rod bent at a 90° at one end and a handle formed at the other end. You can insert the bent end into the ash pan from the bottom door, rattle it around and knock down the ash.
Fireman is using one in this photo.
DPL.
You can see one here behind 20s air pump.
Jeff Taylor
CRRM curator of equipment and rolling stock.