I used to use 1/64" Obeechee sheet all the time in my glider slope soaring days. It's an outstanding way to cover a foam core especially for aggressive sport flying!! It might be too much $$ for me though to do it for such a big model
I've used Japanese tissue directly over bare polystyrene hot wired foam "tube-like" fuselages, using water based polyurethane as the resin. The brown paper method you mention would probably be like a heavy grade Japanese tissue (did he use epoxy as the resin for the paper?) and that would be perfect for a large model like this. Japanese tissue shrinks quite a bit when drying- so while it's a great stressed skin on a fuselage, it can be a possible issue for airfoils in warping unevenly unless done right. I liked it well enough in that there was a lot less of an issue for filling weave, unlike glass. I did not fill the foam voids - just laid down the tissue on the foam and the resin was painted on directly. The one thing I didn't like about it was the surface was not as strong as a proper glass surface but it was very light weight as an advantage.
Thanks for mentioning the paper option. The more I think about it, the more paper seems like it might be a possible option too. Again - a money savings over glass and balsa!! How has your friend's 757 held up over time? Can you share his paper application technique? Did he use paper over bare foam or did he also use paper over balsa sheeting? I'm curious as to how his wings were covered and if he had any issues with warping. Does he use multiple layers of paper, like we would with glass, to build up surface strength?