I did five years as an interpretive smith at Ft Vancouver - (a rebuilt Hudson's Bay Company outpost) Luckily we had a million-plus artifact inventory to choose from to try and determine forging technique by direct examination.
Even though this is a company that has an unbroken chain of records going back hundreds of years, and there were reams of info on what was made, quantity in stock, what to charge for them, where they were shipped, who bought them etc., there was virtually no written record of "how-to" regarding blacksmithing. The company however did make sure it had very accurate record of how much material and time a smith should spend on each item so as to keep predictable margin on each product. It was a situation where masters and journeymen were hired, specs and requirements were given but techniques and methods were transferred only within the walls of the smith's shop amongst the workers. Even in a perfect record keeping environment, smithing techniques never seemed to make their way to paper.