Grantaire takes charge, naturally.
Makes sure Jehan, Courfeyrac, Musichetta, Marius, Joly, and Bossuet are armed with several guns and know how to use them. Gives Bahorel a lead pipe, keeps a fucking machete for himself (“we can’t waste bullets, boys”).
Combeferre and Joly become the most valuable, because they’re doctors. Cosette and Jehan make runs into cities to steal supplies because they’re the fastest and because Cosette’s fucking vicious with a knife. Never uses a gun if she can help it; she hacks the zombies to pieces. Marius is more than a little terrified of her.
Eponine teaches everyone else how to shoot. She and Enjolras team up a lot, because if they were to stay with their significant others they’d just totally lose their shit trying to keep them safe, and Combeferre and Grantaire are both very capable. Feuilly and Marius hunt; Bossuet is learning from Combeferre and Joly so that he can help if, God forbid, something happens to one of them. Musichetta tends to go off on her own and come back covered in blood and grinning because she’s a fucking hero; when the time comes she probably pulls a Michonne and drags one around behind her with its jaw ripped off.
Grantaire is a fucking god in this world
he sets zombies on fire for fun
this is what he was made for