I bought used Big Dipper off ****, and when it arrived it was caked on the inside with about 1/8" of dried lacquer and a solid 2" plug on the bottom. Thought I would chip off the worst near the top, then fill it with solvent and let it sit for a month, empty it and see what happens. I grabbed the top edge of the crust with a pair of pliers and started twisting, and twisted, and twisted, and twisted and the whole mess came out in one chunk. Couldn't believe it. Sometimes it's better to be lucky than skilled.