Matt, when doing "rough-in" of the wires to the location they're needed, I used bread-ties to hold things in place temporarily. Bread ties for us are tiny guage (18-20?) metal wire with a plastic coating over it. Works great and if/when you need to add a wire or two, simply twist'em open, add your wire(s), and re-close.
Later when you're happy with it, wire tie or tape it permanently into place. Removing the ties along the way of course!:LOL: