This was an idea I had a few years ago to make the Military Grade Denier Molle Pouches waterproof and more rugged...
The idea worked out well. I used the pouches you'll see in the video as bicycle panniers to carry gear in and I rode the bike across the US through the elements, spending weeks outdoors.
Would I use Plast-Dip spray again to add extra weather proofing to heavy denier material? yes
Was it absolutely neccessary? probably not, but glad I did it.