On my Cordura boots I have had really good luck with the Tek-Wash brand stuff, but the kind made for boots. It works well to make the boots waterproof and still breathe a little bit. But, there is one caveat: It does not work well if there is a lot of contact wetness. So, if you are walking in the rain and shallow puddles you will be OK, but try walking through tall wet grass and it will force the water right into the cloth.