I use this method with good success - leave the fork assembled, drain the fork oil, flip the fork over and press the fork downwards - the more pressure the better. This compresses the spring against the damper rod with enough tension to (usually
) stop it rotating as you try to undo the damper rod retaining bolt. Use a rattle gun for best effect. Giving the damper rod retaining bolt a hit before you start with a drift also helps to break the lock. Good luck.