If you are at the point where you need to start unhooking sections of the daisy-chained gr-bl wire to help you find your 10 pt short, then yes you should separate the run of the wire at some roughly physical half-way point in the daisy-chain. Always separate the run at a solder lug, of course. If your short goes away when you isolate a section of the daisy-chain, then obviously the problem is somewhere in the isolated section. Once you have found a fairly small section that contains the short, you should be able to track down the root cause at one of the connection points for the wire.
Generally speaking, you can assume the short is not inside the wire cable itself. That does happen once in a very rare while, but it is extremely uncommon - it usually only happens if the cable got pinched or crushed or damaged in some other way. So if you inspect the length of the cable and there's no sign of trauma, the fault is very likely to be at a switch.
On a Williams game of this era, to check voltages you can clip one lead of your voltmeter to the common terminal of the transformer. This will be the terminal marked "C" with several yellow wires soldered to it. Alternatively, you can clip to any nearby wire in the game that is yellow, since that will be directly tied back to the "C" terminal of the transformer. Then, you can check for 25 volts with the other lead of your meter. Be sure the meter is set to AC voltage, not DC voltage.
- TimMe