I received my preloved Trousse 28 last week and it was in amazing condition but the zipper was a little stiff. I didn’t want to risk breaking the zipper pull so I did the old “wax paper trick” 
This trick has made the zippers on my pochettes, toiletry pouches, wallets - zip smooth like butter.
It has definitely freed up the Trousse’s zipper some but it isn’t as smooth as I need to feel comfortable not possibly breaking the zipper pull.
Any other tips for a sticky zipper that I can try??

This trick has made the zippers on my pochettes, toiletry pouches, wallets - zip smooth like butter.
It has definitely freed up the Trousse’s zipper some but it isn’t as smooth as I need to feel comfortable not possibly breaking the zipper pull.
Any other tips for a sticky zipper that I can try??