I'm in the process of stripping, detailing and painting a friend's old Key GS-3, and it has the typical Key drawbar arrangement, with spring, screw and drawbar, and a bronze spring wire to contact the pin attached to the tender offset from the center of the pin hole in the drawbar.
This particular drawbar was bent up pretty bad and the spring around the mounting screw between the drawbar and the body was squashed and otherwise deformed badly. When I removed the drawbar, the spring actually was in two pieces, and since this is a critical electrical connection, I decided to mount a new spring when I re-attach the drawbar again, but I'm soldering a super-flexy black wire from the drawbar to the loco body for a more robust electrical connection.
I've got a resistance solderer, so soldering the stranded wire to the brass body will be easy. I'm not sure it would be as easy with just a hot iron.
I'm also considering blackening the nickel silver drawbar and bronze spring with Neolube, which will also enhance the parts' conductivity.
Cheers!!
Bob Gilmore