Thanks to all for your suggestions and comments.
I filled the voids this afternoon; some of them were quite deep. I just kept pushing the "coff-oxy" into the voids until no more would go in. We'll see how it comes out.
Mike, I like your idea of reversing the top and bottom, and may give that a try when I get back to turning this. Thanksgiving is probably going to mean a pause in woodturning, but after that, we'll see what happens.