The old mountain biker's trick after "3D Violet" (*gack*) passed out of fashion vogue. I don't know how effective such a thing will be on the hard-anodized coatings used on some lights. This works for the more common decorative anodizing.
Oven cleaner, like Easy-Off. It's a mild sodium hydroxide solution that will strip through the anodized layer to the substrate in a sufficient amount of time.
My caution and disclaimer: I used to work with stronger NaOH solutions for cleaning aluminum vacuum deposition "overspray" from production equipment. I'd recommend wearing safety glasses or goggles, and good rubber gloves. HaOH is another term for caustic lye. You don't want to get this stuff all over you. If so, rinse quickly, rinse very well, and rinse again. In case of excessive contact, acetic acid (vinegar) can be used to help "balance" the pH of the NaOH and make it less harmful. Then, as mentioned, rinse. Alot.
Remove springs, switches, seals, lenses. Excessive exposure of aluminum to NaOH can have adverse effects on the aluminum, so go easy, spray-and-scrub, and rinse thoroughly. Take your time and repeated applications rather than to try to strip it all off at once.
That's just my experience and comments. Others may have other views or experiences.