i use diggers fiberglass resin, pick up bout 500mls for 17 bucks from bunnings, n 1litre for 25-30. fibreglass mat and cloth from bunnings as well. if you want to save money on your brushes buy diggers acetone from big w for 10 bucks. for bondo go to autobarn, you can buy a kilo for 25 bucks. i have seen four kilos for 50 bucks but it depends what you use though.
i have even tried using builders bog, the stuff meant for fixing your walls when you want to fix your walls. its good, but when it dries its real brittle. dropped from the same height bondo works alot better at keeping your helmet together. just my two cents worth