Just check out this
https://richardscustomrifles.com/products
I saw the DVDs and flipped through the book.
Just to be clear - the techniques applied are in some ways still the same but for sure every gunsmith has its own preferences, how to set up thier building processes/ machinery etc. Some use CNC machines, some use good old school lathes etc.
Initially, I got an education as a "electro mechanic" (direct translation of my first profession), where I learned some basics about metal work incl. milling, drilling, turning etc.
I'm still in the process to gather and learn a lot about the SML builds, as I'm "forced" to get my own build done due to a bunch of governmental oversights in the US and CZ, which makes it very expensive to get a finished build delivered.
I had also a lot of very good conversations with some builders and folks around here to learn about this stuff.
Also was checking the gunsmithing books available but not really something around for SML builds.
Some nice vids out there on YouTube.