For my half propane tank processing pot with cylindrical sides and a curved bottom, I use a cake icing spatula. The springy, flexible blade makes scraping the sides and bottom easy. Mine is a straight blade, but the offset types I'd bet would be even better. The rounded tip actually helps with the curved bottom. The tip could be cut or ground flat for the bottom and inside bottom angles of a casting pot.
Available here, at BB&B, or at your local Good Will store.
https://www.amazon.com/Straight-Stai.../dp/B07CVQHBSS