One of the things I’ve tried with a J3 attack is a minor IC in FIC (thats french indo-china if anyone was wondering :-)) I also break off a chunk of the fleet, usually 1BB 2DD 1CR 1AC with 1ftr and 1 tac and several transport and place them off the coast of FIC, then posture with the rest of the fleet in the carolines, so they can respond to any major allied build up. The real key is to make sure you have Yunnan under your control at the start of turn 3. This way your airforces can strike at India proper.
From these positions you can hit the allies in all of their IPC rich tt and damn near double Japans Economy in 1 turn. Also, with the IC in FIC, you can create a self-sustaining front, allocating resources there using IPC take from the region.