Tip: Make a party with two of the required characters + a fast group damage dealer and you can clear the character usage missions while also farming the required monsters.
Bomb x40
Note: the Summer Fiesta co-op event Summer Incursion Dawn has 3 bombs in the first wave, so you can farm them easily there.
Story Act 1 Chapter 2: Ominous Shrine Ruins Pt. 2 (Normal difficulty) has 6 Bombs in 3 waves. You can complete the mission in 8 fights.
Alternative:
Palom’s Lost Chapter: A Mischievous Black Mage Pt. 2 (Normal difficulty) has 5 Bombs in 3 waves. You can complete the mission in 8 fights.
Thanks
To the DFFOO “Monster Hunter Guide“, an initiative to list all monster locations in the game (maintained by Marvan09).
To @xcaliblur, @mzpro2 and @infinitus who also contributed tips for these stages in our public DFFOO Telegram group, which can be found here: