I would use 18 or 20 gauge wire and just go from the track to the switch and back up. DC is not as particular as DCC, and you are probably asking this question because you are reading a lot about special wire sizes for a DCC layout. And, you will probably only be using one DC loco at a time (maybe two at the most) in the section you want to switch off.
Not quite with you, if you are after isolating track ends, ok you need the wiring(ouch).
If ,you want to stop a train with 1or maybe 2 locos on the front of a train, then you don’t need any, just gap 1 rail far enough away from the track end to accommdate the locos and solder a diode across the gap. The locos run onto the dead end and stop, when you reverse direction and the doide lets the power flew and they pull back, remember you get one heck of a mess when pushing stock.
It’s that long since I did any, I can’t remember which way round the diodes go, best bet try one, if it keeps going, turn the diode round and you’ve crack it.
This is foe DC only, if I’ve mis-read you, then I’m sorry for waisting your time.
Why does he need to go “back up” ? What prevents him from running a single wire from the + terminal on his DC controller to a place where he branches out wires to one terminal of all the electric switches and then run one wire per electric switch up to the layout, where the wire is soldered to the + side track in each isolated section?
Thank you, Elmer, for your kind & thoughtful reply. I wasn’t so concerned about the wire gauge as I was about the power feeds; will I need them to augment the length of wire running to the switch & back? Irealize that the switch itself is unpowered…