You can buy some Nikwax that is a spray on type. You would just spray it on the outside, let them dry, wash them and then use. That is not too expensive, however, I have an even cheaper option. I bought some Silicone Water-Gaurd from Walmart for 3 or 4 dollars and I think it works just as good. I used it on the outside of several fleece diapers and some pul diapers as well, and no leaks. It has been a few months, with several washes a week. And I almost always wash and dry on hot. Even if this stuff only worked for a few months I think it's worth it. It was in the sporting good section. Hope that helps.