Geof has kindly sent in this advice to help others in the hobby.

Working in N scale requires a steady hand, particularly when painting small plastic parts or details on structures or vehicles. I have found that using your typical rubber molding compound as a masking agent can make this work much easier. I have a number of the Woodland Scenics structures that, if painted in two or three tones (broad colors for the overall structure with detail painting for windows, doors, trim work, etc.) can be very difficult whether you have a steady hand or not. I paint the detail work first (window sills, frames, doorways) and then come back and carefully apply a heavy coat (or two) of the molding compound directly on the painted surfaces after it has dried over night.

Then, after the rubber molding compound has dried (a few hours), I can spray paint the larger areas for a nice, uniform surface. After this second layer of paint has dried well (over night is best), I pick at the edge of the window sill areas or whatever with a toothpick to work the rubber compound free of the model.

Using my fingernails or a pair of tweezers, I find the hardened rubber pulls away very easily from the model. You may find that some small areas require touch up repainting where the rubber molding compound was applied too generously but if you were careful, these areas are few.

It takes a little practice but I have found this technique works best because I have found without it, the two (or three) different colors tend to smear into one another as one dissolves the adjacent color(s). This tip works for any scale (obviously) and only on plastic. It MIGHT work on other surfaces like cardboard or paper but I have never tried it.

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