John Allen wrote an article on how he achieved the "sway-backed"
look on his rolling stock + some other great tips on weathering in
the January 1956 Model Railroader article entitled; "AGING AND
WEATHERING CARS AND LOCOMOTIVES". "Using a simple wood jig and steam
from a teakettle, you can "build in" a sway or hump on old cars.
Here, too, is how to paint a locomotive firebox so it looks like it
is hot, and how to paint on those white deposits of boiler compound
around the whistle and pop valves".
Oahu Ry & Land Co.