Hello,
When I was heavy into 1911s (and I mean obsessed, like I am now with muzzleloaders), the man I was learning from (I'd use "apprenticed to", but it was not a formal arrangement, and he was kin besides) gave me some basic instruction.
I practiced a few things on cracked frames and slides.
Then he gave me a used, but uncracked, frame and slide one day, and a parts box. Told me to assemble a working 1911.
Wasn't hard, and he died shortly thereafter. I was one of his hucklebearers.
I began learning on my own after that. Never did fit a beavertail but once, so I figured I'd just build a MEU(SOC) 1911 to carry. It worked, and it shoots fine.
I'm finding it's a lot like that with muzzleloaders. It's really just been a CVA Bobcat and a CVA KY replica thus far, but both have been torn down and are back together, both working better than when I brought 'em home. (They were used).
Tomorrow I'm supposed to swap for a T/C New Englander .50, and that might be a bit of a different ballgame, but I don't expect it will be too different.
I plan on buying a boxlock and building a target rifle around it one of these days. That should be some different, but still the same principle.
My advice, rather than to watch a video, is to first get a .22 you don't mind messing up, take it apart, then reassemble it. Then find a cheapo sidelock ML you don't mind messing up, totally strip it down, then reassemble it.
You'd be surprised at the dexterity you get with the practice, and how much easier all firearms will be, especially after the .22.
I've honestly never seen a firearm that is not based around one of three or four basic operating systems. (I'm not talking operating types, but rather how the hammer engages the sear, locking systems, etc. All can be actuated by different means of course - lever can do a tilting block like an SKS, but it can also actuate a rotating bolt, like your average bolt action. A caplock is just a single action, like on a Colt 1873 revolver, or Ruger single action, etc, or even a modern revolver in single action mode or even a 1911 - forward, half cock, full cock, not much to it).
Josh