The enemy of your food storage is time, heat, light, moisture, oxygen, and pests. Storing grains in a sealed Mylar bag void of oxygen, in a food grade bucket, in a cool place is one of the best and cost effective ways to quickly and inexpensively build your food storage.
This is the best way I have used to store grains long term. I use 2 500cc oxygen absorbers instead of hand warmers (but hand warmers will work).
(addendum – I would not recomend hand warmers because they lack food grade packaging)
If you do not used a vacuum of some sort to pull out the excess air, then get out as much as you can by hand and use 3 500cc oxygen absorbers.