White light - dangerous as it gives your position away yet absolutely necessary if the shooter is bound legally and / or morally to identify the target. Weapon mounted systems offer the most direct control of light orientation with respect to muzzle alignment and allow for a full final grip on the hand gun and forstock control on the shoulder fired weapon. The down side is that it is a bulky package but apparently not that bulky as many Law Enforcement students of ours have Sure Fire Mounts on their weapons. Most importantly with this configuration one can anticipate that a shot fired near the light center will probably result in a hit. Big problem! That's why I am a proponent of IR systems but this is not practical for the everyday situation- it's really the easy way out of a controllable solution.
With any white light assisted low light shooting training, it is absolutely imperative that the student is taught to use the light intermittently in very short bursts, only long enough to orientate position and identify persons or objects in view. The shooter must be prepared to make the shoot / no shoot decision immediately than change position as rapidly as possible. This takes a bit of practice as the walk and chew gum syndrom usually takes over here.
The Surefire Training Institute has an excellent program that focuses high power light (i.e. 520 Lumen power and the like) as a debilitating technique to blind the opponent (or any one else for that matter). It makes sense but I can't comment as I have never been in a combat situation with this technique. I can say that their Z12 is one powerful hand or mounted light and has many uses that conventional lights don't have. It is, after all, as powerful as an automobile headlight. Think of that hitting you in the eye in a dark room.
The old FBI extended arm technique probably wasn't a bad technique when you consider shooters were not using a weaver grip in those days so the weak arm was used as body armor and independent light holders, etc. I still can't believe how difficult it was for me to swallow my manly pride and use two hands to grip that tiny hand gun. I can assure you Walt Marshall had his hands full when he trained me up at GS Ranch.
Rolling the flash light doesn't warrant a conversation other than to say if it works for you - use it.