This is kind of an old thread, but a couple things I'd add, since I helped a friend do this in a storage container not so long ago.
I second the one way only containers, by the time they are selling those containers for cheap, you can assume they are falling apart from rust, and will have a LOT of small and not so small holes show up over time.
Before anything else, rent a sprayer (if you don't have access to one) and spray a heavy coat of paint on the container, inside and out. Be safe when spraying paint inside it of course. If you had the cash and access to the stuff, I'd spray or roll on a coat of truck bed liner all over the outside and on the floor inside.
If no access to the bed liner, then consider spray polyurethane insulation if its available for the outside (not the floor).
Instead of cutting styro insulation with a bandsaw, or any saw for that matter, spend an hour or two and make a hot wire cutter. They can run off the wall (with some resistors and such) or some batteries. You probably won't need to do it, but you can even make them quite large if you needed to. You'll be able to cut shapes and sizes with a precision you could never manage with a saw, and make MUCH less mess.
Whoops, I just noticed someone else mentioned spray insulation, I fail at completely reading thread.
