I have been rewiring and rebuilding several postwar locos and wire selection quickly became an issue for me. The OEM cloth-style 24 gaugewire was not really working out for me. I found this wire on the interwebz. I recommend it 
It solders up SO easy-peasy and you can easily separate it into single or double strands - if that is what your application requires. It is the most flexy product that I have found and I have started rewiring any roller pickups and sliding shoes because they are generally 60~80 year old wire that is stiff or cracked. This stuff doesn't bind or limit the movement of the rollers, trucks, or slide-shoes at all! I like using 20 or 22 AWG (instead of the oem 24awg) in the postwar locos because they are usually amperage-thirsty motors, especially the double motored locos. And the black color disappears better than the blue/green/yellow/white/red used from the factory. I do own one modern loco from 2012 and this wire is even more flexy/forgiving than the wire on the tender trucks too.
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