[JasonB]

Whatever you do the main thing is to start off gently, and test your method on a spare, or damaged piece of track.

Avoid harsh abrasives and strong chemicals as the abrasives can strip off the plating of the metal, leaving the rails more prone to rusting, and chemicals can mark or even damage the plastic base.

I usually start off with a soft cloth doused with a little methylated spirits, white spirits, or even WD40. White vinegar can also work, but you have to be careful to dry it off properly. That should smarten up any mild tarnishing, and if you need more, then you can move onto kitchen cleaning pads which are a little more abrasive, but not enough to any damage to the plating.

Rust is obviously a different matter altogether, and if a track is rusted, the plating has no doubt been damaged already. I've used a very fine grade of sandpaper, or a small whetstone to smooth off the blistering that you get with rusting, but this has specifically been to target small areas, not something to use over the whole rail.

When you've finished, apply some rail conditioner such as Inox MX3, WD40 or other magic rail conditioning juice by putting a few drops onto the braids of a car and running a few laps. Maybe also rub a drop of machine oil into those rusty areas as these will be prone to rusting up again.

Good luck.