the usual burst is using a water, and 3 other chars(at least 1 fire)
Shrink is used when bursting in 4 turns

however, substituting a Water with shrink with any element that has cuss(Wit job) JS Skill, preferrably a fire wit, the damage and exp gained will be higher. also, it is in 3 turns only,

it is used when you have 3 rb fire damagers and 1 char/pet to level to 100+. much faster than the normal burst.

sample set up:

fire wit with cuss
1: cuss
2: hf self
3: attack
4:attack (2nd mob)

fire killer/wit
1: def
2: hf self
3: attack
4: attack (2nd mob)

char for burst(any element)
1: buff pet
2: 1st debuff
3: 2nd debuff
4: debuff (2nd mob)