Disassemble the car first - all of the parts can be washed, but the steel weights should at least be exposed to allow them to dry. Generally, only the body needs to be washed. If the car is factory-painted, some liquid dish detergent in fairly warm water will do. Use a toothbrush for hard-to-reach areas, and if the car has mould or mildew on it, add a little bleach to the wash water. Rinse thoroughly when finished and allow to air dry. I'd recommend not placing the car in direct sunlight, as the plastic can easily become hot enough to deform severely.
I use the same procedure for washing new cars and locomotives prior to painting.
Wayne
Assuming the car and it's markings are water proof, and if memory serves, the Trains Miniatures were all molded plastic which is water proof, then soap and water is a good way to go. I use an old toothbrush to scrub it gently, and 409 cleaner to cut the crud. Rinse well. I put the car out in the bright sun to dry. I might see if I could take the car apart before washing to allow the insides to dry. You don't want the inside to fill up with water and stay wet forever.
If soap and water doesn't get it off, I might try a rag moistened with mineral spirits (paint thinner or charcoal lighter fluid). I would avoid any of the strong solvents (MEK, lacquer thinner, acetone) lest they remove the paint and attack the plastic.
David Starr www.newsnorthwoods.blogspot.com
I use a old soft shaving brush and water with a drop of Dawn dish washing soap.I rinse and dry with a hairdryer set on low.
Larry
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"