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Stopping any recurrence of the rust.
Usually, on a steel tool, I'd recommend keeping a coating of WD-40 on it (I do this with garden tools), but that's no good here, because you're going to be breathing air that has passed through the wand. And breathing WD-40 fumes would probably cause you to mutate....
I'm thinking thinned-down Rust-O-Leum, swirled around the inside so that it coats the entire surface. POR-15 might do the same thing, but it might be too thick. POR-15 is a paintable rust-stop coating (the letters P-O-R stand for "paint over rust").
One thing's for sure - rust returns unless you take preventive measures. Any other - hopefully better - ideas here?