I use Mineral Oil for short term. Have not needed to long term store.
But my casting mentor keeps his stored in 9x13 ish tupperware containers molds submerged in 90wt oil.
I have used his molds a hundred times. They come clean for use pretty easily but require good soap n water hot wash clean and a heat cycle. But never a lick of corrosion.
I like the idea/suggestion of mineral oil coat and vac seal and then in a 50cal metal can with oul soak Cardboard bottom n sides...
Right now, I use a roll around steel tool chest from Harbor freight. Tops area I have found a "snack container" tupperware like, that fits my Accurate/Arsenal/MP molds well with area for extra pins. In top.
Drawers are full of LEE then largest, two bottom drawers have two 12x14x4.5" double sided "tackle boxes" providing approx 12 2x2x2 partitioned spaces. In each drawer. Able to comfortably hold two, 2 cav Lyman or RCBS/Saeco/Lachmiller molds in each. Then in bottom, I have a couple
more larger but single side "tackle boxes" for the larger 4 cav Lyman molds molds.
All coated well in mineral oil. No problems in half doz years like that. Before that, I had molds in factory boxes wrapped in oil soaked t-shirts.
CW