Farming middle is way less time consuming, just pray that you don't run into metal gods or totems since they will ruin your score by 1m+
Some tips:
You need all the buffs you can get: Crit rate/crit damage(griff)/spark dmg/atk up/bbatk up/add element/ignore deff
A well imped/sphered Mifune is a must, hopefully breaker, I'm using blighted seal on him(+100% atk and +50% crit dmg, from trial x2) and a spark sphere, make sure that his one sbb hit sparks with your other units

Leader/Friend: Probably Crit damage up like Griff or Kira/Dion.
Now get to work bitch!
