Install spray-on truck bed liners by using a paint spray gun on a clean and dry truck bed. Before beginning, it is important to wash the truck bed using a car soap that is free of any wax or other protectants that could affect the liner's adherence.
Use 36-grit sandpaper to rough up the truck's bed and help the liner adhere. Remove the resulting dust with a dry cloth. Use painter's tape and paper to protect the areas adjacent to the bed liner from overspray.
Some manufacturers require that you apply a primer or adhesion promoter before applying the spray-on liner. Be sure to follow the recommended application technique and drying time if that is the case.
Apply the first coat of product to the truck's bed using a spray gun. When using a spray gun, point the nozzle approximately 18 inches from the surface, and cover the area with a single light coat applied in a sweeping motion. Test your spray gun technique on a piece of cardboard before applying the first coat to the bed.
Allow 10 minutes of drying time before applying a second coat of liquid bed liner. Continue applying layers of liquid bed liner until you reach the desired thickness. Apply a coat of liquid hardener if required by the manufacturer.
Wait for the finished bed liner to dry slightly before removing the painter's tape and paper.