In Canada, go to Walmart and get Super Clean. It's in a purple container. It MOSTLY works. I say mostly because I have some varnished stuff that just won't come off (soaking for weeks at this point).
OTOH, other stuff, even varnished stuff, came off quite easily. It doesn't seem to harm
GW plastics, but for safety's sake put it in a glass container and use eye and hand protection, or you'll get chemical burns.
Note I tried Simple Green and 99% Isopropyl Alcohol, and neither of those work very well. I understand the formula for Simple Green was changed recently so people recommending it probably mean the old formula. Don't bother, go straight to Super Clean. Try soaking it for 4 hours and see how much that takes off, then try longer if you need to.
See this thread for more details:
https://www.dakkadakka.com/dakkaforum/posts/list/737067.page#9585032