Thanks for the question.
Yes, it is possible to store prairie fire crabapple berries though it takes a bit of effort. However not all birds are attracted to them so don’t be disappointed if certain birds take no interest in your offerings. In looking through various websites and similar to your experience, I found very little useful information. I then consulted some of my birding colleagues for ideas. They suggested the following:
1). Make sure to harvest the berries when they are fully ripe. They should be plump, colorful, and have a slightly sweet fragrance. Only use berries that are free from any signs of damage, mold, or disease. It sounds as if you think that this is now true.
2). Carefully remove any stems, leaves, and/or other plant material from the berries. Wash the berries in cold water to remove dirt, debris, or insects. Using a colander, drain the berries. Repeat this washing and draining process at least four or five times until the berries appear to be completely free of any extraneous material. You may have to use tweezers to pick various things out of the berries.
3). Then dry the berries. This is perhaps the most important step in order to prevent any fungi from subsequently growing on them. The berries can then be air-dried or, better yet, pat them dry with paper towels. Do this drying several times, always using fresh paper towels. Divide the dried berries into several airtight containers or resealable freezer bags. If you have the equipment to vacuum-seal these bags, all the better.
4). There are two ways to store them: freeze or refrigerate.
If you want to store the berries for an extended period, do not immediately bag them but put the cleaned and dried berries in a single layer on a baking sheet and freeze them until they are firm. Then, transfer them to airtight containers or freezer bags. They then can be stored in the freezer for up to 6-12 months.
If you plan to use the berries within a few weeks, you can store them in the refrigerator. Keep them in an airtight container or fully sealed bag and place it in the refrigerator's crisper drawer. They should then last in this state for at least two weeks.
As I first said, I’ve have had no experience with these storing procedures. I am solely relying upon the experiences that others have shared with me. Good luck. Sounds like a very fun project. Get back to us with any further, related questions.