Hold guard until your character flash blue light. Your stun rate for next attack is doubled. To inflict status ailments, the help section on the game will explain to you how to inflict each status ailments

Quickstep will pop a soul out to the field. Be noted however that souls from quickstep are limited

Mystic artes grants souls upon use. The amount of souls depend on the level of mystic artes

Once you've unlocked your 5th party member, you will get a feature called Switch Blast. Switch Blast use 1 BG and switch place with characters that are in the sub party. Character switching in will get 1 soul. This is useful to trade your BG for soul and this will encourage you to use other characters other than velvet. (Switch Blast will also remove status ailments and get you out from being stunlocked)

Pro tip: use this title to increase BG regeneration rate (there should be the same title with different names for each character)

Once you have unlocked your 6th party member, you will get a feature called "Guard Break".

Simply hold down your guard button and wait for your character to flash red, then your next attack will break your enemy's guard and a soul will pop out to the field. Additionally, your stun rate will also increase with Guard Break