FG'ing a Scratchbuild

As the title says, I'm looking to reinforce my cardboard scratchbuild with fiberglass on the inside. I'm sure this question isn't new, and I've seen various threads when it comes to FG'ing, but since I'm a complete newb and have NO experience whatsoever with the stuff, I'm really just wondering if something like a Bondo FG kit will do the job I'm looking for. I welcome any advice on how to handle it as well, should anyone feel inclined. Thanks!

I have a Bondo brand "all purpose fiberglass repair kit" that I've used for the inside of my vacuformed gauntlets and resin cast helmet. It's pretty simple, just follow the instructions but a word of advice: INVEST IN A RESPIRATOR (not dustmask) that can filter out the fumes.

Alright, sounds about what I was thinking--and I'll definately keep the respirator in mind. I didn't know you could use FG repair kits on resin casts as well, so that's good to know. Thanks, man!