Any kind of painting on rails may be a problem if not done carefully. The paint pens need to be shaken almost until your hand falls off from fatigue before they work "as advertised". Also, Testors (who owns Poly S and Floquil) actually marketed the pens to military modelers long before they began the model rr push. I would advise against getting WD-40 anywhere near a model railroad, it may make the plastic parts of ready made track degrade and sometimes turn to gum! Beware. The Vaseline trick soulds OK probably but the best way is to carefully use the product and you will have minimal cleanup. I did a product review for a magazine on the pens and tested them on various model rr things without problem. Later, I gave the pens to Mopman, who may inject his 2 cents on the subject. If painting the rails causes embarrasment when the train don't run...consider onboard batteries and radio control, then the train will run, even across a concrete floor, painted rails not a problem at all!
Yeah, I'd stay away from WD40. It can get gooey. I've used vaseline in the past, and that can be a pain to clean too. Lately I just use a little LaBelle oil (safe for plastic version), to help keep paint out, and it lubricates the point rails at the same time!
