I would try a piece of laminate which can be broken to leave a sharp edge,
it should not scratch the surface.
Lubricate with Mr Muscle kitchen cleaner, keep scraping & squirting,
changing the laminate when the sharp edge wears off.
I used a window scraper, the kind with a Stanley knife blade sideways on as
it were. Use a new blade, go steady and you won't damage anything. I also
use the same implement for scraping the remains of gaskets off car parts,
just in case that tip ever comes in handy.
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