Inside-out pillowcase tied tightly, put into an insulated box with some loosely balled newspaper or shredded paper. Tape up the box so drafts don't get in. There is plenty of air in the box, no worries.

I would use either a 32qt tub or the 20 long for a 2ft snake(actually I would use a 15qt tub, but I know ya'll like the bigger tubs/tanks).