I get an average of 5 used guitars shipped to me daily. It is a lot easier for me to check the guitar out if I don't have to do a setup first. By loosening the strings as much as people do they usually blow the setup, Sometimes even bridge saddles fall out and cause damage to the guitar. Loose styrofoam beans are useless for shipping anything delicate. They always settle to the bottom and basically offer very little protection against anything.
Bubble pack is the best bet.
Even wadded up newspaper is better than beans. It's good to make sure the guitar cannot move inside the case . Usually a little bubble pack at the headstock area will solve any movement problems. Make sure the case does not flop around inside the shipping box. That will cause a real lot of damage.