Just for clarification have you done this method on the hand guards?
I ask because I've found it doesn't work on all plastic parts: I've done a few bumpers successfully but some of the trim on a Jeep didn't react.
R
I've done it on all trail bike plastic panels/mudguards etc. including hand guards, chickened out on a fuel tank though ....because it was still half full!

and the tank, the clock surrounds, the cables, back of the indicators, handgrips

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