To apply and sand car filler effectively, first clean the surface with a degreaser and dry it thoroughly. Apply a thin layer of filler using a putty knife, pressing firmly to ensure adhesion. Allow it to cure fully according to the product’s instructions, typically 24–48 hours. Once cured, sand the filler gently with 80–120-grit sandpaper to smooth it with the surrounding panels. Repeat sanding with progressively finer grits (220–2000) until the surface is level. Finally, wipe away dust and apply a clear coat for protection.

The process demands meticulous surface preparation to prevent defects like peeling or uneven finishes. A 2021 study by the Auto Body Repair Journal found that 65% of filler failures occur due to improper cleaning or moisture, underscoring the need for pre-treatment. Sanding with the correct grit sequence ensures smooth integration with the car’s body, reducing the need for multiple applications. Data from the Professional Auto body Association (PABA) reveals that 90% of professionals use 120–220-grit sanding for optimal results, balancing removal efficiency and surface quality. Skipping intermediate grits often leaves micro-scratches, requiring additional refinement. Curing time is critical; insufficient drying leads to weak bonds, as noted in a 2020 report by the National Association of Body Shops (NABS), which linked 40% of post-cure failures to inadequate drying. Thus, following structured steps minimizes rework and ensures durability, aligning with industry standards for automotive refinishing.