Yes, using a clay bar before polishing is highly recommended.

Here's why:

1. Removes Contaminants: Clay bars effectively remove surface contaminants like brake dust, industrial fallout, tree sap, and other pollutants that regular washing might not eliminate. These contaminants can cause scratches and swirl marks if not removed before polishing.

2. Smooth Surface: Claying creates a smooth surface, which helps achieve better results when polishing. It allows the polish to work more effectively, enhancing the shine and clarity of the paint.

3. Prevents Damage: Polishing without claying first can lead to dragging contaminants across the paint surface, which can cause more damage than improvement.

4. Better Adhesion: For products like waxes or sealants applied after polishing, a clean and smooth surface ensures better adhesion and longer-lasting protection.

So, using a clay bar before polishing is a crucial step to ensure the best possible finish for your car's paint.