Machine versus hand: what each tool can and cannot do
The workhorse of modern polishing is the dual-action (DA) machine. Its head spins and oscillates at once, which spreads heat and makes it very hard to burn through paint — the tool most mobile technicians should be running for most jobs. The rotary polisher, spinning on a single fixed axis, cuts much faster and suits heavy correction in experienced hands, but it concentrates heat, bites at edges and creases, and causes most of the horror stories in this trade.
Hand polishing has a role, but a narrow one: working a small etch mark, applying glaze, or finishing spots a machine cannot safely reach around door handles and mirror caps. What it cannot do is genuine correction across a whole car — human arms cannot sustain the consistent pressure needed to level clear coat evenly. A 'full hand polish' at machine-polish money is really a wax-and-fill job, fine only if described and priced as one.