Panel bond will work. Basically its liquid plastic that hardens. You will need the gun also to apply it. Sand it down repaint. Your having painted correct
3M™ Short Strand Fiberglass Reinforced Filler
Bondo® Bondo-Glass Reinforced Filler, 00272ES, 1 Quart
ROBERLO 66257 RESIN GLASS - FIBERGLASS REINFORCED POLYESTER PUTTY
3M™ Milled Fiberglass Body Filler
83 Pickup restoration, Page 3
Specialty Fillers Part 2 - Fibral Lite - U-Pol
Contains chopped fiberglass. Repairs holes, cracks and tears in fiberglass. Repairs holes in metal. Smooth spreading. Waterproof. Can be used with 3M Fiberglass Mat or Cloth material, part numbers 05837 and 05838.
3M 05816 Short Strand Fiberglass Reinforced Body Filler
Bondo® Hair Long Strand Fiberglass Reinforced Filler
3M Milled Fiberglass Body Filler, 05816, 1 gal : Tools
Dynatron™ Dyna-Glass Short Strand
Bondo® Hair Long Strand Fiberglass Reinforced Filler