Fill the resin container on the resin gun with the specific type of fiberglass resin needed for the job. Mix the resin with a 4-foot drill mixing attachment and an electric drill.
Put on a pair of rubber gloves and fill the catalyst container on the resin gun following the directions in the manual. Close the lid and secure it.
Put on a respirator and connect the resin gun to an air hose that is attached to an air compressor. Make sure all the air pressure gauges on the resin gun are at the levels the manual recommends.
Spray the gun into a bucket to make sure the catalyst is coming out of the tip and the gun is spraying correctly.
Spray the entire surface of the part you are applying fiberglass to in a heavy mist. Apply the first complete layer of fiberglass material to the part and saturate it with resin using the spray gun.
Evenly spread the resin onto the material using a felt roller. When the entire layer of material is saturated with resin remove any air bubbles from underneath the material using and air roller.
Repeat this process until all the layers of material are applied to the part. Let the fiberglass harden.
Clean the tip of the resin gun thoroughly with acetone and a paint brush immediately after you are done using it. If the fiberglass hardens in the tip it will cause damage and possibly ruin it.