Polyester (fiberglass) resin is less expensive but more toxic (wear a respirator) and shrinks as it cures (affecting your part sizing). Epoxy resin is a little more expensive but not as toxic, doesn't shrink, and is stronger than polyester resin. Either can be used with fiberglass mat/cloth for strengthening a hardened piece. People have also had success with using thinned wood glue to harden their parts, which is not toxic at all but not as strong as resin. The main thing you'll want to avoid is getting the paper too wet and it deforming during the hardening process. Don't harden the entire model in one go, and if a model includes supports, use them. There are a number of introductory threads on the forum and you really do need to invest some time in reading them for gaining a rudimentary understanding of the process. There are also some great videos out there, such as Cereal Kill3r's and BenStreeper's, plus many more on YouTube. Welcome to the asylum. :lol