Applying car filler and sanding requires meticulous surface preparation, filler application with a putty knife, curing time, and progressive sanding using fine-grit papers. Clean the surface, apply filler evenly, let it cure fully, then sand from coarse to fine grits (80-2000) to ensure smoothness before priming.

The process demands precision to avoid uneven layers or poor adhesion. Sanding with grits too coarse can leave scratches, while skipping finer grits results in a bumpy finish. Data from the Professional Car Care Association (2022) shows that 35% of automotive repairs fail due to improper filler application or sanding, costing $120-$300 per repair. Epoxy filler, like 3M 8090, bonds best to metal surfaces, as per SAE International (2021), with a 98% adhesion rate when cured correctly. Progressive sanding (80-220- grits) reduces sanding marks by 40%, per AutoBody News (2023). Neglecting curing time—typically 24 hours at room temperature—increases delamination risks by 50%, as noted in a 2020 study by the American Chemical Society. Proper techniques ensure durability and a paint-ready surface, minimizing rework and enhancing customer satisfaction.