Philpat,
Maybe this will be a little late to help on the silver track sections? Here is what I did with my PZ IV that came with the shiny metal tracks. First I tried the vinegar soaking. On the first soak, I wasn't to happy so I tried it again. Came out a little darker, but still to metal looking ( I could have painted them here and they would probably look good) I then used Perma Blue gun bluing. It came out perfect ( see the pics in the thread PZ IV outside ). One thing you want to do is scrub the tracks really good if you use the vinegar wash first. It seems that it produced a bit of scale that the bluing didn't cover, so I blued them again after scrubbing them. Hope this helps you and anyone else who has the shiny tracks.

Jim