How to properly use the staff?

[Nemesis T03]

What does it mean by bonus damage on skills refreshed?

[Army of Optimists]

When you charge, every tick of the charge counts as an attack and will countdown skill timers. If you recharge skills using the ticks, the final blast deals extra damage.

[Mejwell]

The quick attacks are fairly useless except for maintaining mobility- rely on your charge attack because:

-Each attack that occurs while charging counts double for refreshing skills
-The charge attack will hit all enemies in the cone, ticking multiple refresh counts at once, which paired with the above recharges skills extremely quickly
-Each skill that is refreshed by the charge attack while it is charging causes a burst of damage on full charge which is the "bonus damage on skills refreshed" you referred to.

You don't need to do the full charge every time (although you get that burst of damage if you can), stick and move and do charge zaps to refresh your skills, and then use your skills so that they can be refreshed again, and do full charges whenever you can get away with it. Skills that can hold multiple charges can help with proccing the bonus damage on skill refresh.