I think I would go to the local home improvement center and pick up some rolls of #18 rip cord, so called because it is a 2 conductor cord designed to be ripped in two to separate the wires (lamp cord wire). The #18 gauge wire will be bigger than the wire that comes with your Lionel switch machines, but since you are running it 25-40 feet, the larger wire will keep you from having voltage drops from your control panel to the switch machines. If there is an electrical supply wholesaler near you, I like to use the electricians alpha numeric marker tape to mark my wires and then a short piece of clear heat shrink to seal the markers on the wire. That makes it much easier to locate specific wires and know where they go if you need to trouble shoot a problem later on. Get some regular heat shrink tubing just big enough to fit the over one rip cord conductor ( probably 1/8-3/16 inch), then solder the wires from your Fastrack switches to the rip cord and use the heat shrink for an insulator afterwards. Use 40/60 rosin core electrical solder to make connections.