While explaining the "how's" and "why's," I thought it would be a good idea to share this with everyone. This is the humble beginning of "Fred's Tub Packing Tips."
The first questions were addressing particularly fragile items. Sometimes requested items are old and brittle. Sometimes they are just so dog-eared from repeated reading that they are falling apart at the seams (literally.) <-- (See what I did there?)
My first suggestion is to determine if it the item should be loaned. Sometimes not sending it may be the best way to preserve it. That decision will vary from library to library and what is being requested.
My favorite solution is to re-purpose an old shipping bubble bag to hold the item. This is a good reuse of an item that generally gets tossed by many libraries. Notes can be written on the bag and it can be continually reused as long as viable. Also, repairs to the bubble bag are as simple as using some packing tape to reinforce a seam.