I rehydrate in freezer bags using Sarbar's cozies.

For rehydrating in a pot or a bowl, you can easily make cozies from Reflectix. Anti-Gravity Gear makes pot and Ziploc bowl cozies out of Reflectix, but you can make your own quite easily. They are lighter and less bulky than the blue foam.
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey