How to Sand Auto Body Filler for Painting (80, 150, 220, 320 Grit Guide)

Body filler (Bondo) is a must for repairing dents and dings before painting a car. But even the best filler job looks bad without proper sanding. Each grit plays a role in shaping, smoothing, and blending filler into the surrounding panel. This guide explains how to sand auto body filler step by step using 80, 150, 220, and 320 grit sandpaper.

Why Sanding Body Filler Matters

Body filler hardens quickly and must be shaped before it fully cures. Sanding removes excess material, feathers edges into bare metal, and creates a surface that primer and paint can bond to. Skipping grits or rushing leads to waves, pinholes, and visible repair spots.

Tools You’ll Need

• 80–320 grit sandpaper – coarse to fine for shaping filler.
• Sanding block or longboard – ensures flat, even sanding.
• DA (dual-action) sander – speeds up larger repairs.
• Body file (optional) – for initial shaping before sanding.
• Guide coat – reveals low spots that need more sanding.

Best Grits for Body Filler

• 80 grit: Rough shaping immediately after filler sets.
• 150 grit: Refines filler surface and feathers edges.
• 220 grit: Smooths surface before primer.
• 320 grit: Final step for a seamless paint transition.

Step-by-Step Process

1. Shape with 80 grit. Sand filler while still slightly soft to remove high spots. Stock up with 80 grit (50-pack).
2. Smooth with 150 grit. Feather repair edges into surrounding metal. Use 150 grit (25-pack).
3. Refine with 220 grit. Levels surface for primer application. Stock 220 grit (100-pack) for shop use.
4. Finish with 320 grit. Creates a paint-ready surface that blends perfectly. Use 320 grit (10-pack).
5. Apply guide coat. Lightly mist with contrasting paint, then sand to reveal low spots needing more filler or sanding.

Special Cases

For deep dents, apply filler in thin layers instead of one thick coat—each layer should be sanded before adding the next. For small repairs, you can start at 150 grit and skip 80 grit.

Pro Tips

• Always sand in long, even strokes to avoid waves.
• Use cross-hatching patterns to maintain flatness.
• Don’t rush to 320 grit—each step removes scratches from the last.
• Check your work with your hand—your fingers can feel imperfections your eyes miss.

Aftercare

• Apply primer immediately after sanding to seal filler from moisture.
• Inspect under bright light before painting—imperfections show more once painted.
• Store sandpaper in a dry place for consistent performance.

FAQs

• Can I paint directly over filler? No—primer is essential for adhesion and protection.
• Do I need to wet sand body filler? No—only dry sand. Wet sanding softens filler and clogs paper.
• What happens if I skip grits? Deep scratches from coarse grits may remain visible after paint.

Watch & Learn

For flawless body repairs, stock up from our full metal sanding collection.