I have added light pickups to over 20 Lionel trucks over the years. Here is some details of how I do it. They do not back up real well over my 31 Marx 1590 switches but work great in forward. I do not know about Lionel switches.
I made 5 cabooses with electrical pickups for lights in the last two months. I started making them starting 30 years ago,with a few cabooses and made two 4 car strings of Lionel 2400 passenger cars for bodies and bought roofs and window panels, building the frames and adding trucks with homemade light pick ups and am still at it. I buy all the trucks I can find at train meets also.
An electrical pick up was made for one of the plastic O gauge trucks. My method using a piece of thin brass shim to make an electrical pick up was used. I have made over 20 of this hard to find pick ups for my train collection.
Picture of outside rail pickup, simply wires wound loosely around the axles
From another write up on OGR
I added a homemade light pick up to one of the trucks, made from brass shim stock and a piece of tin can for durability. The pickup must be no wider than 3/8 inch so it will not short on Remote Control track sections. I use trucks without working couplings to have room for pick up. The white wooden block is glued on with E6000 glue and serves to move the pick up back and provides a place to put a small screw to hold the brass shim pick up. See the folded edge on the shim to keep it from moving side wise and the plastic of the truck extends out past the wood block.
Ground wire on the other truck for the Christmas tree 12 v light bulb and a socket that was mounted in the cab.
It may sound like a lot of trouble to make them and have not heard of many others making them but I have it down to a couple of hours each while watching the TV news etc.
Do not over look the use of 12 v mini Christmas tree lights and sockets for rail car lights. These are cheap and use less power than the lights Lionel used in their 2400 series passenger cars, at two lights per car. Cheaper than regular incandescent bulbs too. LED lights are lower in power usage but cost much more.
Charlie