Make sure to grind and bevel the edge from both sides,before laying up the cloth,so it doesn't show the ghost line in the finish later.Try to avoid using resin to build shape or fill voids.Without fibers,it becomes very brittle and will chip easy.I would recommend using epoxy resin,you can pick it up at any marine store.Use chopped strand cloth,not weave.If you have voids and low spots, you can fold the cloth a few times and cut it up,stir it up in resin and you have solid filler. Z-Grip is a good filler that doesn't cost $50,it's around $25-28 per gal.