A while ago I helped someone using Laharl as their main for this battle. IIRC they did have some perfected items/max attack, but I think you should be able to do it as well, even with non-perfected stuff.

tl;dr: safely position the pringers in a 3x3 formation. Stay far away from their aggro range and build up combos with Gig (without moving him) using normal attacks and counters with your other units. When you're ready, buff him as much as you can (5x Braveheart, have Rozalin/Majin Hanako next to him before attacking, have Miabel out etc), throw him into position (again, don't move him on his own or you'll lose the bonus) and attack. Maybe use some Kunoichis to build a combo before attacking for an extra push and/or save at least 1 char to lift Gig in case some of the pringers survive (just remember to use a different move next turn if that does happen).