In other matters, I'll go with resining my armor. However, it wasn't the resin my dad was worried about, it was the cloth. So instead of glass cloth, we'll use gauze, or some old rags. Still don't know about the bondo. I might go with my paper mache pulp idea.
The resin is clearly the bigger health hazard here.
Fibreglass also doesn't just "come loose" once you've properly applied it.
I'm not sure you can replace fiberglass cloth with rags.. or gauze.. if I were you, I would get some rubber gloves, and use THOSE to handle the fiberglass!! or use fiberglass chunks!
You can. But the reason for doing so wouldn't be that you might otherwise touch the fibreglass, but rather that you might breathe dust particles of it.
Here, maybe this will help you decide: http://www.405th.com/showthread.php/33426-Prop-Making-Safety-Guide