I've had the best luck from heating the bezel with a heatgun, to around 150 degrees F for several minutes. This is uncomfortable to hold, but not to the point you burn yourself.
Once the assembly's warm, I wrap the rubber from two strap wrenches around the top and bottom of the bezels, clamp down two sets of pliers, and twist. The rubber should be thick enough to prevent damage to the anodizing, and gives plenty of traction.
Once I feel the adhesive give way, I can usually use the straps and my hands to open the head the rest of the way. Less time near the pliers means less chance of damage.
The adhesive Fenix uses is pretty brittle, so it's easy to remove from the threads once you have things open. I use a small flat-blade screwdriver to push out the big chunks, and reassemble and disassemble a few times to get the little stuff.
