I taught a number of techniques for tactical use of the flashlight to hundreds of officers. We ended with night fire on a blacked out range, which by the way requires some extraordinary safety protocols. Although multiple techniques were taught, students naturally gravitaed to the Harries and FBI techniques. At CQB range, the light is on the support shoulder or tight next to the shooter's head on the support hand side.I practice the Harries method most and I prefer a light in the 150 to 300 lumens range. My current bedside and jacket light is a Streamlight protac dual fuel. My EDC pocket light is a an Olight 03t aaa light which throws a 180 lumens using.an Energizer lithium, I carry a spare battery in my pocket too.
I find lights over about 300 lumens to create too much reflection off vegetation and light colored walls with my very light sensitive eyes.
In my young days as an officer we carried 6 cell Kel-lights and I later had a baton light. They were great defensive weapons but would now be regarded as deadly weapons so most PD's don't allow them.4 D cell Maglight, hit 'em with the battery end, it's heavier and you won't damage the reflector.