Hi, I got my $2 lighting circuit perfected for installing lights into my passenger cars.

Here's one on adding lights to a Walthers Dome car, without exposed wires going to the dome: http://cs.trains.com/mrr/f/88/t/282261.aspx
Here's an OLD post on figuring out how to solder wires onto those tabs on a walther's car: http://cs.trains.com/mrr/f/88/t/252113.aspx
Here's one where I install lights into a Branchline Heavyweight: http://cs.trains.com/mrr/f/88/p/259248/2910544.aspx
Lastly, in order to install pickups, I just use a brass (copper is better) sheet, bent into shape to touch the axles of the wheels. There are much better methods but this is my cheap and easy way. I recently have been using Walthers metal trucks, which can pickup power from both sides of the track, using all wheels. In this case I just simply add a brass washer to the truck screws and solder a wire that goes from there and through the frame of the car.
Here's a shotty video of me in the middle of upgrading my P70 coaches with Walthers trucks, and flicker free lighting (and other upgrades).
https://youtu.be/umMfs_HiODY
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That all being said, I have yet to bother installing markers into my cars as of now, but it should be as easy as wiring them parallel to my LED strip with a 1k resistor. Finding the castings for those markers will likely be the hardest part.
Cheers!
Charles