Argh... SOOOO MANY RESIN QUESTIONS!!!
Seriously there are like at least 3 ongoing threads covering this. You guys need to do some homework. Go to your local Home Depot or Lowes, or Auto Parts store, buy a little kit and read the instructions carefully and follow them.
Polyester (Fiberglass) Resin : $30-$35 a gallon.
Bondo: $20 -$25 a gallon
Brand names don't mean a thing. Bondo brand or not, it's the same thing chemically; Polyester Resin and Methyl Ethyl Ketone Hardener. Go with Elmers brand if you like... get whats cheaper. I've never noticed a difference between brands.
Sanding it with a average paper dust mask... um sure, if you like inhaling toxic dust! Those masks let a lot of particulate matter into your airways because they aren't form fitting. They're better than nothing I suppose, but you should really get a proper respirator is you're going to be doing a long-term project like this.
Alright? Can we have a truce on the Fiberglass/Bondo questions for a while?