sean,
I thought you where doing a day for night thing and didn’t realize the footage was shot at night. I would go with what Arnie wrote. Because you are only adding the smoke (Moon never touches ruff) I would duplicate the video clip. Add a mask to where the smoke touches the roof only. Place the smoke and a cut out of the moon in-between them. Work with the black sky you already have. Then you only need to worry about a mask around the small part of the roof where the smoke touches it. Best of luck.
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