LA's Totally Awesome. Or if you want to use a real paint stripper. Mostenbocker's lift off. Neither will eat plastic. Mostenbockers will soften it a bit if you leave it too long.
Totally awesome is fairly basic and can, undiluted, cause a mild chemical burn over a long time. Not a big deal, but if you were using a bunch for a long time, if wear gloves.
Soak them in a jar with Totally awesome for a week. Should come out almost entirely clean. There is a video from Goobertown hobbies where he tries several products. IIRC they soak for a month.
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