I am using several flashlights for finding swirls and impurities on car paint. LED's are great for this purpose but the task is not as simple as it sounds. There are too many variables. One flashlight that works great under some conditions may fail under other conditions, even on another panel of the same car, even during the same session. The curvatures of the body, the resulting shades and reflections and my own angle of view play me visual games that may be quite misleading.
Sometimes a powerful flashlight shows the defects that a weaker flashlight cannot. Sometimes the opposite happens. Sometimes a flooder works better, sometimes a thrower. In my experience, there is no single flashlight that shows them all at all times.
My favorite pocket light for this purpose is my Niteye 10 TIC. The infinitely adjustable control ring enables me to find the right amount of light. I play with the ring all the time. At some point, it eventually shows an impurity that was otherwise invisible. This sweet point changes all around the car. I also keep my Preon P0 handy. Its pure flood proves useful in some cases but a little more power could be beneficial. A Preon Atom, for instance, could be more useful in complimenting my Niteye 10.
If you are a professional car detailer, you may, perhaps, consider dedicated swirl-finders like Brinkmann or Flex but I have never used one so I have no experience with them. I am not sure if I am allowed to post a link but you can find them via Google.
Sunlight is the ultimate swirl-finder, though. Besides, nothing is "strong enough" when it comes to the sun! I use flashlights only indoors to see if further corrections are needed or if some streaks or spots remain but eventually, I pull the car out for the ultimate control.
I hope this helps. Good luck!
P.S.: Headlamps don't work for me. The reflection just blinds me. I always need a different angle of illumination than my angle of view.
