Nothing special needs to be done to preserve them. Here is my process -
Drill fairly large holes (something like a 5/32 or 11/64th drill bit if the nuts are large enough).
Let them dry that way for a day or two - at least until any moist areas have dried up.
I like to use shoe laces to string mine. They hold up well and are easier on the neck than something smaller. You can get them at the Dollar Store cheap (a dollar if I remember correctly).
If the lace wont go all the way through use a smaller drill bit to push it.
You can find scarlet and gray beads at places like Michaels. Lots of folks use white instead of gray. That is WRONG. This is tOSU - not IU.