This made a very smooth filled joint. I did this both from the inside and outside. This was all a cheap experiment. If it failed I would not be too disappointed. But it was amazing how strong it turned out.
Newspaper has a 'grain' and so it tears easily along one direction only.
So each alternate layer of newspaper would be 90 deg different. PVA Aquadhere didn't seem to glue well straight to foam. In between every 2 or 3 layers of newspaper I'd make a layer of random, very long strips of 'drywall' or 'gyprock' jointing tape. By about layer 5 or so, I knew it might work, or at the very least, be a good release layer for fibreglass. By layer 6-7 I knew I was on to something.