Sorry, but there is no walkthrough. For the big war in Chapter 4, I suggest you set up your line in the order of:
1)Aragon 2)Dax 3)Damien 4)Xaveria 5)Shi Long 6)Dyluck 7)Galadria 8)Caranthir 9)Cosmaterra 10)Zahra Fiarai 11)Badmosche
3, 6, and 9 should each have a "Fire All" spell, which will ensure that one of them is present in every battle against the Red Skeletons. If not, substitue with someone who has a "Hit All" spell/attack.
Also, Demons are weak against water and holy. Also, buy Dax's Boomerang from Erdrick at the Inn, if you can afford it.