Having done a lot of stuff with casting resin, I have a valuable piece of advice for you. What you need to do is take your cup and chisel the cured resin out of it. Once your cup is reasonably clean, you'll need a broad tip felt marker and a piece of cardboard.
Now take all of it to a busy street corner with lots of pedestrian traffic. Once you get there, sit down, set your cup on the ground in front of you, and make up a cardboard sign that reads, "I am a prop hobbyist, please help."
I hope you find this tip helpful.
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