I stumbled into a package of industrial size cotton swabs at Orischeln farm supply store. I paid $6.00. They are huge! And just the right size for cleaning out grubby old inserts.
They are called Grip 325 pc Industrial Cotton Swabs.
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Amazon has them but they are too pricy.
Ebay search term: Grip 325 piece industrial cotton swabs
They are selling on Ebay, but prices are all over the place from $8.00 to $15.00. Shop wisely.