Hello all. I'm new here so forgive me if I'm asking a question that's already been answered. I'm just getting started in HO model railroading and have purchased one of my Holy Grail engines, "The General" by Mantua. This kit comes unpainted in pot metal, and I've heard about soaking such kits in a vinegar bath in order to lightly etch for painting. What is the makeup of the bath? Is it straight vinegar, or is it mixed with water? Or perhaps a nice balsamic with olive oil? I understand too that I should wash the non-electrical & non-moving parts afterward, but wouldn't this promote rust? Thanks again.