Excellent info Bob. That Panel Liner is exactly that: A type of a wash/stain. I also have recently started playing around with it. It comes with multiple colors. Black is good for deepening locmotive grills, but for surface details I think the other, less stark colors like brown or gray work better for a realistic look. Going by the smell, those are some sort of oil-based stains so the solvent might affect certain paints used on the model.
