Dual Action polishers are characterized by the motion of the head. It spins on a central spindle, and this spindle rotates around an eccentric offset. Polishers are also called orbital polishers for this reason.
The rotating and orbiting of the pad prevents the polisher from burning the paint, which refers to removal of paint below the clear coat surface. Dual action polishers produce very little heat compared to a rotary polisher.
The same safety feature which reduces the possibility of damage from a dual action polisher also prevents it from removing very deep scratches. While a dual action polisher will improve the appearance of scratches and remove most swirls, it does not produce enough heat to cut deep into the paint.
If you need deeper scratch removal, this will require a rotary or circular polisher. Keep in mind, rotary polishers in inexperienced hands can quickly burn the paint. The pad spins at high speeds and it's up to the operator to keep the polisher moving at all times. If the polisher lingers for a second too long on one spot, it can burn through the paint.
Dual action polishers will improve the texture and luster of automotive paint with virtually no risk. They are the most user-friendly option for beginners and professionals, and they consistently produce beautiful results.
Note: Scratches that extend below the clear coat should be repaired by a professional. Attempting to remove these deep scratches could result in removing too much clear coat and causing the paint system to fail.