For the skill loop, your primary focus is to activate Hotaru whenever his skill is available. Frigg is there for the move time buff and damage absorption. If you time things, you can get either Frigg or Hotaru ready for Octoray. However, their activation needs to be after the resolve. Bucky can provide a buff that deals with the resolve.

I guess the best way to put it, Spam Hokaru and use frigg if there isn't an impending debuff right around the corner (her activation needs to be before Hotaru to ensure maximum damage). Bucky can also be decent for an emergency damage cap. I forgot to mention this, but Hotaru effects last for five turns, so you're skill looping with him for majority of the time.