Can you rehydrate phyllo dough?
I think rehydrating evenly is going to be very dicey. Instead, when you first open a large pack, immediately separate it into smaller batches, wrapping each tightly in wax paper and then a zip-loc removing as much air as possible, and re-freezing those smaller packs. Now you won't have to thaw and refreeze any sheets more than once - just grab the number of smaller packs you need. This should keep them in better condition.