In my experience it can be chipped/chopped/gouged/peeled away. On a relatively soft lead figure, some pre-treatment with a chemical stripper (oven cleaner, etc.) may be advisable to loosen it up first. When stripping painted figures, I sometimes find that green stuffed additions will simply fall away quite naturally during the stripping process.
I'm not aware of any products that will specifically dissolve green stuff, although acetone may help (some professionals use it to get a smoother putty surface when they're done with their sculpts).