Question on how Barber’s mechanic works

I’ve been playing a bit over a month or so and am still at Paragon 700. I have been leveling and trying out various classes and builds to see what I enjoy playing most. I am currently working on a Mundunugu’s Spirit Barrage build. Still accumulating the set, so I am running a LoD version to farm the remaining pieces I need. My question is about how the Barber’s mechanic works with accumulating explosion damage. Should I be spam clicking on bosses or holding down and releasing after a few seconds to build up damage or what? I can’t seem to tell what works best.

Thank you! Completed the set a bit ago, and the damage increase was phenomenal. Now I just need to get a ring of emptiness and dial in some stats.

Eh, it’s slightly different now with gazing demise nerf, but I’m too lazy to update it lol.