This method has worked for me.
Take a small block of scrap wood and drill a hole in it the same diameter as the bezel of the ARC. Cut the block in half right through the hole so you now have two blocks with a half circle in each. Wrap the ARC bezel with some tape both to protect it and to increase friction. I've tried friction tape, gaffer tape, rubber tape, masking tape, etc., and they all worked fairly well. Gaffer tape (cloth tape like a good duct tape, but with a matte surface)and linerless rubber splicing tape (rubber electrical tape with no adhesive) worked the best, if you have access to either. Clamp only the ARC bezel tightly between the two blocks in a bench vise and use a heat gun on the rest of the head. Getting the heat right is tricky, I stop when the head is just barely too hot to hold for more than a second or so. Quickly wrap a strip of tape around the knurling on the head and put the strap wrench on and turn. I use a small strap wrench from McMaster-Carr with the strap doubled. I have opened a few this way and it usually takes at least several tries, and one took a lot of torque. If you are carefull, you can use this method and not damage the anodizing.