I would love to hear any tips and tricks on making the harnesses.
Measuring the correct length, looming, routing, documenting the wiring, and such.
Also, what crimpers you are using?

Been wiring a friends car with the Ron Francis kit, and it came with a few rolls of Techflex braided sleeving for the looms.
Been using double wall 3:1 heat shrink on the ends of the sleeving, but had to use electrical tape in a "T" branch, just no way to heat shrink it, like a "Y" branch.
I have been using the MSD ratcheting crimpers with the changeable dies. Spent more on the different dies than the tool, but it does make nice crimps.