1- Altering the balance between physical and spiritual energies in your chakra by disturbing your physical energy. This is done by producing pain. Pain comes from the body and thus it makes your physical energy fluctuate by "shocking" your body. Because of this fluctuation, your chakra flow experiences a spike. This spike is a disturbance that will dispel other disturbances present in your chakra by unbalacing its flow and reseting it to its normal flow. The higher the pain, the bigger the spike. The more resistant or accostumed to pain your bio is, the less effect this has. Kaguya bios for example have a very high tolerance to pain, making them unsuited for this release method. While genjutsu can mimic pain or any other sensation, it will always pale against real sensations. While Pain is subjective, certain guidelines can be followed.
D Rank Genjutsu: Chipping a Finger (like one does as he bites to draw blood for a Summoning Jutsu)
C Rank Genjutsu: Low level Physical Attacks, Bitting a chunk of your Cheek
B Rank Genjutsu: Low ranked Taijutsu/Freestyle
A Rank Genjutsu: High ranked Taijutsu, Stabbing Yourself in minor muscle, Cutting yourself, Breaking Smaller bones, Low level Burning/Voltage, Painful Cold
S Rank Genjutsu: EIG/Sage level Taijutsu, Breaking Bones, Deep Stabs or cuts, Medium Voltage/Burning, Extreme Painful Cold, Bitting your tongue off