Properly prepared material will save disappointments and unpleasant smell associated with the transport.
In case of shipping from country's other than Poland, please dry your material thoroughly with salt.
In order to do that, you will need to gut it and in some cases skin it.
If the animal is big, you should cut all the limbs, tail (if present) and head with cervical spine and put them into ribcage for shipping. Then wrap it several times with foil, until no smell is noticable.
Please, do not carry out any preliminary steps to skeletonize the material.