Fiberglass epoxy is easy to apply. With an epoxy kit, applicator, and some tools from home, you can fill holes and cracks in a few minutes.
Step 1 - Mix Epoxy
Prepare the surface.
Fiberglass epoxy kits usually come in two tubes: the resin and the hardener. Mix these two at equal proportions or as indicated in the manufacturer's instruction. Most epoxy hardens 30 minutes after mixing, so it would be best if you would mix only what you actually need. Create another batch, afterward, if you will still need it.
Step 2 - Apply Epoxy
Dip a small spatula or Popsicle stick and fill holes with epoxy mix. For wider holes, cut fiberglass cloth in the size of the hole. Apply a small amount of epoxy on the hole. Place the fiberglass cloth. Fill the hole with more epoxy until it covers the cloth. Level the epoxy to the surface and wipe excess film. Allow it to cure.
Step 3 - Sand and Seal
Sand the filled area with fine-grit sandpaper and level the area to the surface. Paint if needed. Apply a coat of sealer afterward. Allow it to dry.