a ETG that works well and reads from a steel substrate costs $500+ dollars.
today I detailed a 1997 BMW 5 series in dakr blue, the car was in good sahpe, only 50K, but swirls galore. I tried a medium cut clear coat compound (Valugars clear coat compound, like the 3M PI Medium cut RC) with Pc and lambswool polishing pad. Did it two times, then moved to 3M FI II with foam cutting pad. 50% of the swirls were gone. Total time, one hour, put down the PC, dawn wash, and ZFx + Z-5 X3 with ZFX and Z-6 inbetween.
The owner can live with swirls, as long as the car is shiny, but I can't spend 4 hours polishing the car with the PC to get it decent, too many automatic car washes and dealer washes, need a rotary to get it back. I will get this finish perfect, just not now. I'm going to invest in a DeWalt next year (Watch out NY d, getting license, car, and PrepExcellence school, you'll be paying me the big bucks!.)