Re: Impression from the Albrecht photos
The varnish used on passenger equipment was like that used in marine applications, because passenger cars got washed frequently. Such washing could be hard on paint but a few coats of varnish over it would hold up and the finish would look reasonably well after many washings. Some roads like B&O (until in its death throes in the fangs of the Chessie cat) repainted their passenger cars as often as every 4 to 5 years to assure a fresh appearance.
And yes, back in the day, presenting shiny and clean cars to the traveling public was deemed better by the company brass than putting out something dull and dirty for them to board. But that is for the passenger list. Not STMFC.
However in a few instances, such varnish was also used on some freight cars - especially those painted light colors such as white, yellow or orange. These colors tended to chalk out and wear off rather quickly.
Paint was usually mixed and made on site at the railroad car shops and applied by brush. Quality and color could and did vary from shop to shop. The use of sprayers to apply paint also faced an up-hill battle on a number of railroads holding to older ways, preferring the brush and their own home-made paints. Spraying paint was looked upon as wasteful.
Modern paint formulations specifically for spraying were developed during the 1930s. They also greatly reduced the chalk-out and fading issue as well as provided more consistent color and quality for the roads willing to pay more for such factory-mixed paint. And most did, during and after WW II.