Why paint looks dull
Swirl marks are thousands of microscopic scratches in the clear coat. Each one scatters light in a different direction, which the eye reads as haze. On black and dark metallic paint the effect is dramatic.
Most of that damage comes from washing and drying, not driving — which is why a car can look worse after a year of regular hand car wash visits than it did when neglected.
How correction works
A machine polisher, pad and abrasive remove a microscopic layer of clear coat until the surface around the defect is level. Because the scratch is removed rather than filled, the result survives washing and does not reappear after a few weeks.
Why measurement matters
Clear coat is finite and cannot be replaced. A paint depth gauge establishes what is available before any polishing starts, and a test section identifies the least aggressive combination that works. Any detailer who skips both is guessing with your paint.
What cannot be corrected
If a defect catches a fingernail it usually extends through the clear coat. Chasing it risks burning through to base coat. The honest answer in those cases is improvement, not removal — or a bodyshop.