[Reece]

Agreed. You do it by "neighborhoods." Divide the chassis into small areas and take a close photo of each section before starting. Then finish wiring one area as photographed before moving to the next. Take loose one end of an old wire but leave the other end connected: solder in the new wire and then route it to the other terminal where you finally remove the other end of the old wire. Best way to avoid mistakes. Follow the original lead dress to avoid feedback or hum problems. On a transformer-operated chassis, I like to make up twisted pair from hookup wire for the heater circuit to run from one socket to another where possible, ditto on runs to the power switch, all of which reduces possible hum. Can't do this with series string heaters where it's best to follow the original routing, which tends to put the first audio heater in a spot where hum should be the least.