Rub the gash with a sponge covered with rubbing alcohol. The rubbing alcohol removes any oil, grease or other dirt that would prevent the repair compound from bonding correctly with the floor.
Apply the repair compound to a plastic scraper. Use more than you think you are going to need to fill in the entire gash.
Apply the repair compound to the entire gash. Press it down into the gash to fill it in as thoroughly as possible.
Scrape up any excess compound with the edge of the scraper. The repair compound in the gash should be level with the surface of the floor.
Apply another coat of repair compound using the same steps if the gash is not completely filled in. It takes 24 hours for the repair compound to dry.