This has been very interesting. After studying a lot of photos in Stan Kistler's Santa Fe in Black and White, I think I'll brush-paint the valve gear as Santa Fe did. I'll use very light grey on the flat rods and black on all the joints and on the rods with raised ridges, and then scrape the black off raised ridges after the paint has dried. Then, I'll give the wheels and rods an overcoat of Neolube. I'm getting ready to do some traveling, but, when I return, this will be a top priority. The 2900-Class 4-8-4 with unpainted main and connecting rods (but with the rest of the valve gear painted) will be last, after the 2-10-2 and the 4-8-2. The 4-8-2, being a dual-service engine will get lighter weathering.
I don't want to over-do this, as these are oil burning engines and need reasonable valve gear grime and sand (just as Hot Water described), and boiler scale, but not the heavy accumulation of soot that is characteristic of coal burners. One can always add more if more is needed, but it's hard to go backwards with weathering.
Jerry, my hat is off. Your personal record is awarded ten merits for excellent steam locomotive weathering.
