That's why I don't really like weathering. Every time I clean and polish my locomotives, I can't help but think of that unsung army of cleaners and painters in the early part of the last century - setting off in the early hours on foot and on their bicycles with a pride and determination that 'their' locomotive will be shinier and brighter than all the others.
A nice sentiment. Then again, if you read Martyn Welch's book "The Art of Weathering" (Wild Swan), you will see that even what appears to be the shiniest engine is in fact remarkably dirty. Steam engines are dirty machines, burning coal, spewing ash and soot and oil. The art is to give the model loco the appearance of being well cared for but in fact shows signs of being that fire-breathing water-boiling living machine.
The best cleaners in the world won't have been able to remove all traces of dirt. In a dirty environment, the best they could manage was probably to push the dirt about. It would gather in recesses, awkward areas the oily rag couldn't reach, where hob-nailed boots would scratch and scrape. Gentle weathering brings a model to life. Indeed Martyn shows how subtle weathering enhances the skill of the model builder.
Of course, it's down to personal preference in the end. Rule One applies!