Safety

• Fiberglass is glass. The word "fiberglass" is not a euphemism for some other type of material. The same glass in your windows is made into very fine shards and stranded together with a weaving process. When sanding, grinding, cutting or otherwise working with fiberglass, the "dust" kicked up is very fine glass particles. These glass bits can irritate your skin, eyes, nose, throat and lungs. Always wear a protective paper breathing mask and safety glasses (available at all home supply dealers), and long shirt sleeves and pants to cover bare skin.
  
  

Gel Coat

• Fiberglass is finished with gel coat. This resin material is mixed with hardener and tinted just like epoxy or polyester resin. The tint agent is added like food coloring to the final mix. The gel coat also sets and hardens in about a half hour, so you must work quickly when mixing and applying gel coat to fiberglass finishes. Gel coat can be mixed in any amount, so only make a batch the size necessary for the area needing repair. A small paper cup will hold enough to refinish most scuff and cracks. Larger damaged areas will need more. Think of the gel coat as you would paint and provide enough for a given area.
  
  

Prepping

• Prep the damaged fiberglass and gel coat by first sanding out any imperfections. Reduce the damage to as flat an area as possible. Then use a good-quality de-greasing cleanser to get the area as free as possible of grease, dirt, any petroleum residue, and fiberglass and gel coat dust from the sanding.
  
  

Refinishing

• Apply the gel coat either with a soft brush or use in an air-spray paint attachment on an air compressor. Apply a thin, even layer and allow about 60 minutes for it to cure. If necessary, apply more coats to produce a solid opaque finish.
  
  Complete the refinishing by sanding the area with finer grits of sandpaper until the edges of the repair and the original finish are feathered together. Finish with a very fine grit wet sanding.