Ok, so there is a super easy way to do this, but it requires a bit of set up to accomplish.
First unlock Moongolow, then go to the vizard located in this level and buy his unlock "glass vizard" for 10,000 gold. This lets him spawn in all levels.
Second, defeat the boss in the fifth stage, Cappella Magna to unlock the Arcana "Game Killer".
Now pick Porta as your character (unlocked by reaching level 4 with lightning ring).
Start with the Game Killer arcana.
Make sure you have a decent amount of gold, then enter Boss Rash and run to the Vizard and buy all the weapons.
Then simply kite the enemies and level everything up with chests. You'll do ridiculous damage and the AoE will be insane. If you've been working through the game normally you should have already met most of the requirements. Have fun with easy mode. 😜