You can spray them with your favorite big game lure/scent and then use safety pins or thumb tacks to attach them to stuff all around your tree or ground stand. Works well especially when using a short ranged weapon like a bow or muzzle loader. I also pin them to my hat and hunting gear and spray them with earth or pine coverscent as the cotton holds the scent longer than spraying the clothing or gear directly. It’s not really a survival tip as such and is only of use if you hunt, but it is the most fascinating use for a cotton ball I have ever come up with.