On plastic parts like the model car kits, the chrome isn't plated in
the strict sense of the word -- it is vacuum deposited on the plastic
inside a large chamber.  Little strips of the chrome alloy are bent
in half and hung on the frame that holds the plastic parts.  It has
to do with electrical charge and temperature and vacuum.

It's been almost forty years since I was installing an alarm system
in a plant that did vacuum deposition and auto parts decorating.
On flat items like dashboard writing, where only the letters needed to
be chromed, they used a tape with the chrome foil on one side that was
pressed on top of the letters with heat and pressure.  The wood grain
and colors was also done this way.

Any plating of plastic is mostly done, or was done, by the vacuum
deposition method.

Glen R. Perye Jr.