There was a guy there today by the name of Matthias Zeller who was selling just track cleaning wagons and rolling roads.   I'd never seen or heard of him or his products before.  He's from Germany so maybe this is his first UK show?   Anyway, I bought a track cleaner wagon for £35.   Got it home on the layout tonight and ran it for just a few feet - and it's excellent!  And there I was thinking my rails were pretty clean!   You don't need any fluids with this; he said just replace the pa