Again, the most important thing is knowing when to not 2A. Usually, since you're crouching, the opponent will want to do their jump attack a bit later. This is your chance to 2A them because they're lower to the ground. If possible, try cross-under 2A, since it's safer.
And yeah, don't use 2A against Hakumen's j.2C or j.B. I think his j.C can be beat though.
As for best to use moves when IBing, it's probably a DP. Maybe 5B / 5C. 2A if you need a quick but not too risky move.