There are two ways to deal with swirls - which will be a way of life with a black car. Either you remove them, or you cover them up. Removing them involves polishing. As hwlcd mentions above, the Meguiars 105/205 combination is a long standing duo to attack and remove swirls and light scratches. Be aware, you are removing clear coat when you polish. Polishing is most often done by amateurs with a random orbital (RO) polisher like the Porter Cable 7424XP or the equivalent Groits Garage RO. THere are a number of detailing supply sources that sell kits including all you need to polish and protect your vehicle. They aren't cheap, but follig their instructions, you can do it. The results will last, but black is notoriousfor showing any defect, and you will provide new ones with poor washing technique or heaven forbid, you run it through a cloth car wash. Voila! New scraches and swirls.
The second approach is to use a light swirl remover, preferrably by machine, and smooth over the edges of the marring, which tends to reduce the refelctions that manifest themselves as swirls. Thes products, like Megs swirl remover, the 3m equivalent or the like have fillers that also fill in the scratches and swirls and will make the paint look pretty darn good for a while. It will soon wear off, and the swirls will reappear, and will have to be filled again every month or so.
SO.... what we have here is a pretty dismal picture for those with black cars(including my black 88 Mazda miata). Either commit to a good wash technique and plan on going to a repuatable detailer every 6- 8 months or so, or get good at it yourself and join the ranks of the crazy ones like me. If you aren't crazy now, you will be soon as it will drive you nuts trying to keep your black vehicle pristine.
It is a sickness casued by buying a black car and becoming OCD. There is an alternative..... lower your standards a bit and set realistic expectations for the appearance of your car. Good luck with that. I am one of the crazies out there in all weather making sure my car looks as best as it can. Good luck to you. For more crazies and professional detailers, take a look over on autopia.org. They will show you automotive perfection.
Nighthawk black pearl looks amazing when clean and swirl free, but is a nightmare to keep clean. Just spent a good part of the day with Zymol HD cleanse by hand and the regular liquid Zymol on the buffer. Just picked it up used a few months ago and have had unusually nice weather. Still need to touch up a few chips/scratches but night and day since polishing.
In the end the product used isn't really all that important. There are dozens and dozens of paint polishes of varying degrees of abrasiveness which can remove anything from minor to extreme paint damage depending on the type of machine and type of pad. There are also several different machines that can be used for this kind of work, so the product used on the pad isn't the only part of the equation. Asking which product for light swirls is literally like asking which tires for the best quarter mile when no other details about the vehicle moving the tires is given.
So just to start back at the beginning, what machine will you be using to remove these swirls with and what pads do you have access to?
I will put a plug in for a very effective 'off the shelf' polish that I have been very impressed with. Meguiar's Ultimate Compound is a very capable polish that I would rate somewhere in the middle of a scale between 1 and 10 as far as abrasive levels go. Similar to 105, actually. Probably more similar to Meguiar's #83 DACP truth be told. It is a great mid level polish that works very well with both rotary and DA polishers.
+1 for Meguiar's Ultimate Compound!
My son just bought a black 2005 Mazda 3 that the previous owner had used a car wash brush on. It had significant scratches all over the clearcoat. We used a Porter-Cable random orbital polisher, a couple Meguire's foam pads & the Ultimate Compound to take out 80% of the scratches. This stuff really works!
Here's an online tutorial we followed with one exception - we used Ultimate Compound instead of 105: How to achieve a flawless, mirror finish using Meguiar's M105 and a G110v2