I think a lot would depend on where you were located. Smiths in more heavily populated areas, where some of the more exotic ingredients for more sufisticated finishes were available, no doubt used them. But smiths on the edge of the frontier, or in the more back woodsy parts of the country, more than likely used what was available. I also believe much of the metal work was left bright on many longrifles. But, I have also examined old barrels that appear to be fire blued, rust blued, browned, and one SMR that appeared to have been coated with linseed oil when hot, in blacksmith fashion.
I don't think there is a one answer fits all applications here. I think you will have to research the gunsmith, and or the region, if you are going to get metal and wood finishes correct.
Hungry Horse