Most people say that to tackle Intangirs you need to use stop and hack away. There is an easier way. This requires Gau with the Destroyer rage (Hermes sandals recommended), Echo screens, Setzer, and two other characters you want to teach magic. When the battle starts, Have any character except Gau and Setzer use the Echo Screen on Setzer BEFORE any other action. Follow this up with Gau's Destroyer Rage.
For those of you who know the slot-pause and Joker's death trick, you won't need to read any further.
The Echo Screen you used unrigs Setzer's slot ability so that you are able to get 777: Joker's Death. This instantly kills ANY monster, even those immune to death. (yes, bosses too)
After Gau has cast reraise on Setzer, Start the slots up. The trick to getting 777 is through pausing the game while the reels are spinning. Pausing and unpausing allows you to get a better view of the symbols. Unpausing while holding A will make it stop on the next symbol. It may take some practice, but once you do get the hang of it, it'll be a piece of cake.
The reason for having Gao cast reraise on Setzer is the fact that when the intangir dies, it counters with meteor on the person who delt the killing blow (Setzer in this case).
This trick can net you as much as 10 AP every battle in only about 2-5 minutes (depends on Gau's usage of reraise.)