Having washed several real steam locomotives, I can attest that it is a lot of work. While streamlined engines would be the pride of the fleet, it is certainly possible that they might have missed a few washes. Additionally, the worst part about washing a steam engine is seeing it the next day after running 100 miles and nobody can tell you just worked really hard making it look good.
Your weathering of the rods looks good. I would try to get a little more soot along the top of the engine.
