the method I use depends on the receiving country and the available skills of the receiving party.
say I was to ship a bass to Australia. The USPS or Austrailian Post has a size limitation of 42", so shipping a bass in a case is not available this route and FedEx/UPS/DHL/etc ... would be the fall back unless the receiving party is skilled in setting a neck (or has access to somebody who is versed in this activity)
in this latter case, there is potential to ship a body and neck unattached and make use of the USPS rather attractive shipping rates (about 30% of FedEx!) and leaving the receiving party the task of securing a case plus attachment of the neck/body and final set-up tweaks.
of course not every sale has a situation where I feel confident that this is a viable solution, and e-mail exchange would need to take place to where I did feel confident else I'd rule out the option and potentially lose a sale due to the higher shipping costs.
each country has its unique shipping size limitations when shipping via USPS, so check their international shipping restrictions on-line to see if you have a good fit with your shipping needs and the receiving country size/content restrictions
o - and remember to secure that battery! you don't want a package being rejected because the battery has potential to short in shipment
all the best,
R