Most of our flowers we simply air-dry. We do not recommend spraying or 'treating' them with anything. These types of flowers will benefit with a spray of 'humidity sensitive' hairspray. The best thing to do is simple wrap them in newspaper, put them in a cardboard box and place them on a shelf. They can easily be stored in a garage or closet.
Basements can be to damp and attics can be too terribly hot and dry.
Never store them in plastic. These little moths are called Indian Meal Moths. The best thing to do with these and arrangements that may be contaminated, is to freeze them. Either place them in a plastic bag and put them in your freezer for a week or place them outside in a shed or garage during winter for a week. We always recommend that you dry your peonies and then immediately freeze them for a week before you use them in an arrangement.