Now to clean all the pieces before reassembly!

Shredder Blade - Wire brush to get the rust off and a bit of a sand to clean it up. If there's any really solid nicks in the blades you can clean them up with a file too. In the inside, give it a quick sand, it was mostly just light rust on the inside here.

Casing - Quick scrub here - I used vinegar and steel wool to get any rust. Clean out the two openings with a bit of sandpaper to remove any rust.