Oxalic Acid works very quickly and is surprisingly effective I have used it on tools, parts and it has done a cracking job at removing rust stain on fiberglass decks without damaging the surface.
I was skeptical, but the results speak for themselves.
This is inspite of the fact that I screwed up; I sprayed the growing mold with whatever kitchen spray was on the window sill - killed the mold but I expected it to kill fermentation process.
Anyway, still worked.
Am trying again and expt is now outside and covered up so it can ferment away.