How do body shops remove scratches from cars and what products are needed?

It really depends on how deep the scratch is. Minor surface scratches can be wet sanded with very fine sandpaper (1500 to 2000 grit) with water. Then you would need to buff with compound. Be careful not to hold the buffer in the same are for too long. This will burn the paint. Finally you would need to polish the area with polish and a different pad on the buffer. 3M makes all of these products that work very good. Thanks