another method you may want to think about is, using kurust, you can get it from any good car spares shop, halfords, etc. its primary use is preventing rust, i'm a welder, and i use the stuff after i have repaired something, as a protective coating before zinc primer.
kurust is a runny white liquid, which you paint on to the part, or you could dip the part in it, you then let it dry, it then turns black, and it dont come off easily, it etches in to metal, abit like etch primer. it will turn black on any surface you paint it on, ive had it on my hands loads of times, and its a bloody nightmare to get off, it wont destroy the metal tracks are made of, so is safe to use on them, just wear rubber gloves if you dont want it on your hands.
Tony

"Er, der kämpft und Lebend davonläuft,
Lebt um einem anderen Tag zu kämpfen".