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.
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May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey