Are there additional electrical grounding methods besides static wicks? Static dischargers have high electrical resistance, and work via corona discharge.

So if I understand correctly, what wicks do is limit the voltage that the aircraft builds up. But as the wick is ionizing the air around, I guess this voltage is rather high.

Do commercial, fixed-wing aircraft need any additional grounding method once on the ground, when the passengers are boarding/unboarding for example?. How it's done?

Related: This question is about grounding for hangar storage, and also explains grounding for refueling operations
Many aircraft tyres conduct electricity which also dissipates charges.  The compound contains "carbon black" or graphites.

In the special case of helicopters using a hook to pick up a load from a hover, the wise ground handler will use a rod on the end of a grounded cable to earth the charge.  Helicopters can build up a lot of static and many a ground handler has been left with smoking underpants by not heeding this advice.