One thing that seems to work during the very limited testing I have done is to use one of the new zip bottomed Platypus water bottles. I have carried them for years for drink and water but with the new zip closed bottoms they can be opened up large enough to stuff kit type stuff into the bottle and then seal it closed. The obvious advantage is that you have a water bottle when you remove the kit. My kit is in a fanny pack much of it water will not hurt but sensitive stuff can be stuffed into the bottle for water proofing it. Also storing the bottle flat or full will make it last longer than rolling it up.