It has been a long time since I have seamed sealed anything besides silnylon. I recall using something that came in a small tube, like model glue comes in, and also a small bottle with a felt applicator. The felt applicator was easier to use and it was the REI brand http://www.rei.com/product/603042 .
Permatex Flowable 100% Silicone Windshield Sealant from just about any auto store will work, too, and is cheaper. I've done my packs and tarp with this (the underside) and it works fine. See here young grasshopper:
"Well, it's one louder, isn't it?"