loner,

Two comments come to mind when reading your post. The Ameristep blinds are supposed to be relatively good in wet weather and I can attest to that. However, in a decent downpour they do tend to leak along the zippers. I don' t know of anything per se that can help with that. However, if you are looking for a general water sealant then there is a pump spray liquid that can be bought at most " X" marts in the camping section which can be applied to a variety of materials in order to give them better water repellancy. It is similar in texture and composition to the UV killer commonly sold with Sportswash.