Well thinking your using a coating with a layer of that fiberglass stuff on top, Id expect just a gallon would suffice. But im not too sure on that. It would take me 1.6 gallons by my calculations but thats because im 5'8''.
I suppose you should buy two gallons, if not just so you have some amount of slack, you dont have to be REALLY careful, you still have more to waste.
The best thing I found was simply putting a layer of resin with that liquid hardener (Make sure to do it in small mixtures, if you mix the entire resin can, you will ruin the entire supply) and apply the fiberglass stuff right over it.
Paper mache could work, but it would look really odd unless your skilled, and would have that shiny glow on it, nor that nice smooth texture.
I suppose you can also just layer tissue paper mache with glass powder or something, but that has got to be a safety hazard so nevermind.
Ah well, exspensive resin it is for you.
I want to buy 1 gallon of fiberglass resin with ligud hardener. Is that the only thing i would need to buy? I would use $50 for just resin and im on a tight budget since i was to lazy to make a helmet so i bought a westerfields. But im making the rest of my armor.