I’ve been working on a short story in which learning to fight with a rapier (or more specifically a sword cane) is central to the plot.  Unfortunately, I don’t know anything about sword fighting or martial arts of any kind…which makes writing a semi-plausible scene difficult.  
My normal tactic of faking knowledge is to go to Wikipedia and learning the jargon and then name drop a controversy or debate that would be familiar to insiders.  That works well enough for a scene about police jurisdiction, or about surveying, but it seems insufficient to write a scene about actually teaching sword fighting. 
So I went to my favorite secondary resource for this sort of thing. As I expected, The Modern Rogue had a video on how to fight with a rapier.  This was not surprising as they have videos on krav maga, dagger fighting, whiskey, cigars, hacking, blacksmithing, and spy craft.  More importantly, they track down actual experts to talk to rather than just show casing what they know personally.   The rapier sword fighting video is a great example of the Modern Rogue’s style.