Anyone know what will remove the white residue from plastic - in this case Union Pac #2023 gray roof besides my thumb nail. 
I know on American Flyer equipment a hair drier just melts the white stuff and you wipe it away with a soft rag. No harm done at all to the plastic.
It is mold release compound.
A known occurance on 2023’s and the plastic sideframes that were used on Scout cars and in a few other places.
Major described the fix.
Thank you sir. Will try.