Hudrock

I've clay bared a black car with great success and little to no swirling (that I could notice). The key is using lots of lube and gentle pressure (don't press hard) and go in the in the same direction. My car was fairly new and didn't have much contamination it so if it was really contaminated I could see how this could contribute to swirling.

I love cleaning and detailing my car but polishing is bit much for me personally so I typically take my car to a pro every year or two and have them polish the car professionally and I upkeep it inbetween. A good/quality job typically runs between 300 - 500 bucks (80 -90% correction) and can take a full day or two depending on the detailer. It really depends on how much swirling you have and how much you want gone. You could have all the swirling removed but it would cost a lot more and quite frankly its not worth it for me on a used car thats a daily driver.

My last detail they sealed it with Ceramic Pro Sport (about 60-90 bucks extra) after a clay bar and 2 stage polish. I have been up keeping it with Hydrosilex Recharge so we will see how long it lasts and if it was worth it. They corrected about 85-90% of my swirling and that part was worth it to me and it drives me crazy seeing all that swirling.