I have purchased "unmarked" rolling stock and engines. I then use decals to make them for Texas and Pacific. Most of my rolling stock is modeled after 1940 type equipment.
I use pictures that I down load from the net as my prototype. I have mastered painting the cars and have done well with the lettering, but the logo for the railroad has been problematic. I have had some success with making my own decals but had failures too.
IMHO there is a market for decals of non-popular road names, the big five road names are well served except for obscure variants but finding logos for something like the Ft. Worth & Denver is difficult.
Everybody seems to have trouble with the small data and safety decals of all lines.
Douglas