Choo Choo Johnny-
It would be easier to use the female pigtail adapter (Part #6-82038); connect the plug end to the accessory, the red wire to the center rail and the black wire to one of the outer rails. The wire can be directly soldered to the rail, or you can crimp a 0.187" male spade connector on the wire and then wedge it under the rail.
Gargraves sells the #930B pigtail feeders which consist of a track pin with a soldered wire; simply replace the track pins with the feeders and splice the wires to the Lionel pigtail cable. Gargraves also offers solderless track connectors that function the same way as traditional lockons do; wedge the clip under the rail, then connect one of the Lionel Pigtail harness to the clip.
Hope this helps!
-John