To try to respond to your question, I searched a few sites for info on various oils and boiled linseed oil. I did not find any use of linseed oil as a cleaner. If anything in use on wood, a mineral oil is suggested to clean the surface before applying the linseed oil. Another page indicated that BLO is not boiled, but combined with solvent in equal parts to then be known as BLO.
Some of the YouTube automotive channels love to feature cars and trucks rescued from back fields, junkyards, etc. It is quite popular to preserve whatever original paint is left on these vehicles with what some call..."patina sauce".
In my own opinion, I think BLO is used in part to protect the sheet metal and show off the original color(s).
This mixture no doubt has a cure time, though that might depend on any number of factors.
In the late 1960's Edaville engine house, was all the crews needed for supplies to fire up and operate the steam locomotives. I can remember getting a coffee can half full of kerosene for igniting the pine slabs in the fire box. My father would fill the oil cans from whichever locomotive he was assigned on that day. And there was grease, brass polish and rags. Not much else, winter or summer.
Before we cleaned the locomotive, Dad would run up to Cranberry Valley working the throttle to pull any loose junk through the tubes. The boiler would be blown down and then we'd back down by the water tank and open the front end and (weather permitting) use a hose to wash everything down. Everything would be wiped down with rags and brass cleaned. In the winter, weather situations would dictate how much cleaning was done. In later years (1999 and so) I used diesel fuel on a rag to wipe down the Hudswell-Clarke engine no. 21. Among crews, that little 0-6-0 was lovingly referred to simply as "the Crudswell", though not because she was dirty.
I would think that kerosene or a light oil might have been used in the old days of the Maine two footers. Maybe not so much during the depression when those liquids were in scarce supply.
As I had said earlier in this thread, oil used on a locomotive boiler jacket becomes a dust magnet. A solvent would cook off or air dry and not hold the dirt and dust.
My Dad worked merchant ship boiler rooms in WWII and the Chiefs that he worked for, insisted on clean fire rooms and a clean stack when running. Two things he used to say not easily done with heavy bunker oil. The stories he and his buddies could tell, just a fading memory now.
One last experience is of the artifacts I have found walking the old W.W. & F. Ry. grade. Thirty years ago, I found a pickaxe head, numerous spikes and broken joint bars, bits of cattle guard and even a complete Ford model T radiator shell in the bushes up in Palermo. Along with items removed from Bridgton Junction, some of these rusty relics were cleaned and brushed with BLO. This has helped to preserve the metal and put a slight finish on as well.
