I'd put my money on VPI or VCI paper. Moths don't like Camphor or Naphthalene because of the smell, and many humans don't care for Naphthalene either. On top of that I'm not sure modern mothballs contain Naphthalene. Some sort of insecticide / repellent mixture that's unlikely to have any rust proofing properties.
Naphthalene vaporises slowly and leaves an oily layer on everything nearby, so it does work. But I doubt it's as effective as a designed VPI/VCI product, which can be had with a MIL-SPEC. When the military mothball tanks, they don't mean it literally!
Dave