Les
Are you using O-27 track, 1122 switches and the Lionel PW magnetic uncoupler ????
I built a PW O-27 Christmas layout for my brother and had good results with all of the PW equipment and track. I used #14 gauge zip cord for the main power from the KW transformer to the line buss and then #16 gauge wire out to the rails for voltage continuity. I run a power drop every 6 feet of track and use one continuos common via the outside rail back to the transformer. I use the inside rail for accessories and isolate it from the common by adding a double pice of electrical tape between the rail and the metal tie.
I ran the switches off track power and use phone wire to connect to the switches to their controllers.
For the PW accessories I used #18 gauge wire and ran them back to an accessory bus bar. Some accessories are activated by the isolated rail once the train enters that section of track.
Hope this helps
jeff