Don't worry about the handle rusting, especially if it's just fresh water (saltwater might be a concern). 410 stainless is very rust-resistant. If any water remains inside, it can be flushed out with WD-40 or isopropyl alcohol. Personally, I'd avoid using acetone. If there are any plastic or nylon components in the knife (bushings, maybe), it might damage them.
I agree, there's no need to take the knife apart for this.