White coat of chalk on lionel scout plastic parts

A co-worker of mine was given a lionel scout set. He brought it to work and showed me what the set showed, and any reccomendations for cleaning it up. The engine seems to run fine and theres very minimal rust on the wheels, there sees to be a chalky coating on the plastic couplers and trucks. Its able to be brushed off but it leaves a clear chalky coat underneath. It seems like it could of soften the plastic as well. Does anyone have recommendations? I cant just brush it off because theres still a layer of coating that needs to flake away. The chalky coating is soft enough and can be scratched off with a fingernail. My thoughts are that dipping the parts in a liquid solvent would be easiest but I am afraid it might deteriorate the plastic further.