Help with Janitor/Broom Achivment

Are down to my last 5 achievements for 100% the game. Currently hunting Janitor achivment (Kill all bosses with the broom). Are currently on the second boss and notice that the broom does so little damage and that's no surprise there. So I'm looking for advice to save some time in the long run. Thanks in advance :)

https://preview.redd.it/ekl1j6pt9nyf1.png?width=804&format=png&auto=webp&s=7ce784c186e36651f5f595ef10aa2c44fe3fcf3d