The BEST paint for model-train people (usually resin or styrene plastic) is enamel for models or acrylics for models.

Go to a model-hobby shop and look for brands like Testors, Tamiya, or Floquil. You’ll need just a few colors: Flesh, Black, White, Blue, Yellow, Red and can hand-mix all the other colors with those primary colors. Tamiya has acrylics that are water-based so you don’t have the hazards of paint-thinner.

Paint the flesh first and then "dress" the figure like a normal person… shirt or blouse then pants then jackets and hats.

It takes some practice, but I have done thousands over my years of modeling.