Hi, I agree with Dave that it could be a very bad idea to clean any of the plastic if you are not 100% sure of what you're doing. I don't collect trains, but long ago I knew a collector/trader/dealer who said leave everything alone if youre going to sell it, and WHATEVER you do, do not try to touch up anything by repainting it. My brother restores clocks that are over 100 years old, covered with grime and rust. He gets a ustrasonic cleaner, mixes up a batch, and puts the clocks in with an air hose from a fish aquarium. When he takes the clocks out, they frequently start ticking, either right away or after swishing the clock in the solution. I bought a plastic container (1 litre, 35 oz) of M.G. Chemicals Ultrasonic Cleaner concentrated which says use 10ml per litre for $7.99 at my local electronics supply store. It should make 3,500 oz of the solution, or 100 batches of the stuff, which is more than enough to clean off the rusted engines I bought dirt cheap, if I remember to grease the inside of the motors and don't burn them up. I would suggest that you buy a bottle of this stuff and ONLY use it, and nothing else, to clean your trains if you feel you realy need to. This stuff cleans "soft metals such as aluminum, copper, brass, silver, gold... cleans metals, plastics, electronic parts, circuit boards, ceramics, rubber, fiberglass, glass, and poreclain." If you would prefer to spend a lot of money instead, go to any ritzy jewelry store and they will sell you a little container of the stuff, diluted, for the same price. Jewelers use it to clean all their jewelry. Again, don't clean or "fix up" anything you don't have to if you are going to sell the set (in original boxes of course, the better the box, the better the price).