Some tips on medaforce.
Each medal has a different power of medaforce, for example:
Kuwagata shoots a blue blast, which damages the enemy extremely
Mermaid heals itself and its ally.
Charging your medaforce happens when you attack (little amount) or are attacked (large amount)
When you're in battle, stand still. After 5 seconds or so you will be charging your medaforce rapidly fast.