You now have too much coal lit. It will probably take closing off the exhaust to really bring the temp down. But just for a little bit about 5 minutes should do it. it will remain hot but you will snuff out some of the not completely involved coals... you need to come up to temp slowly. Only about 10 lit coals or about 1/4 -1/3 chimney lit lump, close 2 intakes at about 200°, it should rise another 50-75° and settle about 250-275°...
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