Sorry Iain I hadn't noticed the link , I've now read it
What I can't really understand is that IPA and WD40 contact cleaner completely evaporate so are just a cleaning solution and shouldn't leave anything behind
I'm about ⅔ through cleaning my layout with IPA, what I will do is clean last third with WD CC and see which parts of the layout needs cleaning again first. There is quite a bit to do as the layout has 200yds of track