I think I may be able to help -
first off, folk art are acrylic paints. Acrylic paints will not react or damage plastic. So, if you try using folk art paints, you won't be ruining the plastic, but you may have to strip the paint of and redo if the finish is not what you desire.
I have used ceramcoat and folk art paints on models. I find them thicker than model paints and tend to cover fine details, but if you thin them with much water, they lose their covering and adhesive properties. I also find them to be less durable, and rub off of plastic with excessive handling. I think the density of pigment in craft paints is lower, and the size of pigment particles is larger. That is why they cover well when full strength but dry thick.
My advice - craft paints are fine for structures, scenery, and people. But I would not recommend them for rolling stock. I am sure there are others who would disagree. But I generally don't like to use acrylic paints for rolling stock because I find they do not spray well in a dry climate.
Kevin