You can Miracle Ticket for Satan or Raiko and focus on a Monochrome element I would recommend Raiko since you have a better chance of reaching -40/40 Debuffs than with dark that relies on RNG to pull Dark Amaterasu for the Sniper Shot, furthermore the SR with the Sniper Shot Skill's event just passed, the Re-Run of Koihime.
For Soul I think you'll need Mordred or her EX as always but then again it's thunder so you want to somewhat prioritize on damage, right?

Even though now that I think about it you have Hercules so you're farming her Relic Weapon I guess, that will give you the debuffs you need for any element