How to do a concentric twist wire harness? (Milspec/Racespec)

[Imarvin240]

I have been looking into building my own wire harness, but have come up with limited "how to" on building a true milspec harness. I'm sure I'm not the only one, so I hope starting this thread could lead to helpful info for everyone. And books/videos/websites would be greatly beneficial to all. Also, if a similar thread exists, I apologize since I couldn't find it. Thank you everyone.

This is the most helpful piece of information I have found so far, but it doesn't quite tell you exactly what you do/don't need and exactly how to actually exicute certain parts of the harness. Also, interested in what tools are actually needed.
https://www.rbracing-rsr.com/wiring_ecu.html

Hoping people on here have even more helpful info!