For old nuts and bolts that I may "someday" use again I put them in an empty glass pickle jar and pour ATF (automatic transmission fluid) enough to coat them . Takes a few weeks to get usably unrusty but it keeps them preserved too.
Also have used a "vibrating tumbler" (like for cleaning bullet brass) and some crushed walnut media mixed with a little Brasso mixed in. That can clean overnight , but best to put that noisy tumber on in the garage while you sleep.
