The MC just have a vague idea of what to do, in fact just about every major project he starts in Border Town goes through a lot of trial and error to get it right, be it the army's weapons or even just building ships.
Because while he might not have the actual knowledge of something, he can start with the general idea, and use the scientific method to improve upon it.
(and for something, he can cheat through with the power of Witches)
Like, when trying to figure out the mixture of ore to make the best steel, Anna literally had a list of combinations that went into 1000+ samples.