People usually suggest the bronze only fight in River King Casino chapter Going All In on Expert, but personally I haet fighting Painwheel, so use another options.
One of the options is using a good bronze fighter with good moves for the final boss in a current daily event, but that's not always a good idea since some daily events have annoying fight modifiers.
Another option are some fights in origin stories. They can have very high FS totals. For example final fight in Peacock origin story is almost 20K total FS, and back when I was doing it my highest FS character was somewhere around 3.5K.
Generally speaking a good lvl 40 silver character goes around 3.5K FS and it can usually solo almost anything a story mode throws at you, so fights with 15-16K+ FS are a good point to aim.
Use one high FS character + lowest FS possible tagalongs (lvl 1 bronzes). Aim for fights without too annoying modifiers against 3 characters (multiple lower FS enemies are easier to fight that one high FS). Avoid Dread Locks like plague. Also modifiers working as DoTs (bleed, biofeedback). Unfortunately the latter probably also means avoid using Blood Drive since you run a real risk of dying to self-inflicted bleed and chip damage.
Using characters with high burst damage (Peacock impending agony combo, Big Band corner SSJ+Beat Extend combos, maybe maxed Heavy Reign since when properly built she charges inferno brigade in 2 good combo strings) is also preferable, so you would have an option to try to nuke the enemy if you see them charging BB3 (you save the burst option just for that occasion and use it right before their BB3 goes online). If you run some plinker like Filia who can't do nukes on demand, you will eat BB3 and die with that FS difference.
PS: in the worst case you can opt out of a mission you don't like (by closing it) and it will be replaced with another mission. I usually opt out of bookworm missions this way since I already have all the stories completed.
