Things that boost different bender skills

Question

We know that the moon boosts waterbenders and the sun and the comet boost firebenders.

Are there other things that boost earthbenders and airbenders?

Answer 1

Such powers are not been mentioned in the Comics or in Avatar or Korra Series. That said, the powers from the Sun and the moon can be seen in the negative sense. Because Night leaves the Firebenders vulnerable a lot (the reason why General Iroh asked Admiral Zhao to wait until daybreak for attack again at Northern Tribe in Episode 19) as WaterBenders becomes virtually unstoppable under moon. Similarly, WaterBenders lose a lot of their power to Sun and they become vulnerable (that's why Admiral Zhao continued the attack only in Day). The powers are more like in Cycle, one is bound to overpower another. Earth and Air on the other hand are elements that have no relation with any natural phenomenon in Avatar World, thereby, making them virtually impossible to be boosted unless by Physical and Mental Training. Besides, Air seems to be the only element that is present everywhere, whether a wooden cage, a metal cage, a ship to hold Criminals, or any other ordinary or extraordinary place. This makes Air as a gift to be virtually available everywhere for any Airbender. Even the Fire has its limits (remember the way Pa'li was caged before being freed) on availability.

Answer 2

Unlike water and fire, air and earth have different properties, thus different objects or attributes can boost or decrease their bending.

Airbending relies on feeling the air current, and airbenders use the flow as a booster to their bending. This can be done by an airbender staff or similar items. This is why most airbenders can't fly without a staff.

Airbender staff is a wooden stave used primarily by airbenders to augment their bending. The versatile instruments were a major part of Air Nomad culture and used in the execution of several complex airbending techniques. Staffs were constructed to unfold into fan-like gliders which enabled airbenders to fly while manipulating the air currents around them.

As for earthbending, earthbenders can boost their bending by boosting their seismic senses. Basically, equipping items like hammers, maces or not wearing shoes enable them to boost their bending in a degree.

Earthbenders have been known to use hammers and fans to augment their bending, and it has been stated that the Chinese great sword dadao, a heavy war sword, or literally "big knife", would also be best-suited for a strong earthbender.