In my experience you can use it to clean off paint, but the surface of the resin will be a bit brittle afterwards (and you can easily scrape the surface of with a fingernail)
Leave it too long and it will start acting like the wicked witch from the north.
I use Easy-Off oven cleaner. Spray the piece and stick it in a plastic ziplock bag. Leave it for a few hours. Then scrub it off with a scrubbing brush.
Castrol Super Clean you can get it in the automotive area of Walmart...
Either give it a bath in a small container, or use the ziplock bag suggestion above for a few hours...
After the paint falls off drop it in a bath of clean fresh water for an hour or so to help remove any soaked in cleaner residue and you should be good to go...