moonlitflies,

I never use thread furled leaders. I only use Vanish Fluorocarbon Gold due to a furled leader from this material really sinks and takes my streamers and other sub-surface flies down deeper. As an experiment one day, I used bow string wax on both legs of the leader before twisting and then allowed it to furl. It is pretty simple and quick to run the bow string wax up and down both legs and then twisting and furling them. I used bow string wax because it will waterproof a bow string and I figured it might work on a furled leader. The leaders I made were made for a raffle so I do not know how they worked out. One could use the soft paste wax that is sold for waterproofing boots. It would be easy to rub it into the thread legs before twisting them. I also read somewhere that one person hung his thread furled leaders up and rubbed them with a rag that had varnish on it and then allowed the leaders to hang until dry.

If you try any of the above, please post your results here so others can give it a try.