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You need a container that can be sealed well enough such that desiccant bag(s) will work. I use these Husky tubs from Home Depot; https://www.homedepot.com/pep/Husky-20-Gal-Professional-Heavy-Duty-Waterproof-Stackable-Plastic-Storage-Container-with-Hinged-Lid-in-Red-246842/311485319 You can put a bunch of spools in there with these huge desiccant bags; https://www.amazon.com/dp/B0DMDW96SV

Everyone has their own solution. Mine is rather simple using Husky tubs; The hygrometer is UV resin glued to the inside. De-hydration is done via fairly massive 600g desiccant bags; https://www.amazon.com/dp/B0DMDW96SV