3M Bondo
3M Bondo Liquid Hardener 1 Tube 0.37 Fl Oz., Use with Fiberglass Resin for Auto
A nice touch is the snap-on plastic bracket that mounts securely without screws.
3M Bondo OR-QT-ES 6 Pk 28 Fl Oz Container Size Pink Body Filler (BW)
You will find that the 6 inch size reduces the risk of tipping over on uneven surfaces.