Choose a container. Wrap the part in plastic wrap. Place in the container and fill the container with expanding foam/insulation from a hardware center. After it has hardened, trim to fit the container as needed.
If you do this, resist the urge to get the foam for large cracks. And be patient. I did this very thing shipping some Hemi exhaust manifolds and found that the large crack foam produces huge holes that don't provide support. I also found that layering it in layers thicker than about 2" prevented the foam from completely curing. It would skin over and even days later, the interior had still not hardened. It'll work but it's a slow process.
