Oh hey we got the same stick :P
I remember that when I wanted to get consistent IAD's, I set specific goals in training mode, like getting 5 consecutive IAD's in a row, and starting over if I messed up. Then I would raise the bar and make it 10 IAD's, and then finally 20 in a row. It's honestly just a matter of doing it enough times that it becomes natural, and in your case since its in the midst of a combo try to isolate that section. I'm pretty sure you can set counterhit on and set the dummy to jump for 5C> IAD> j.B to connect by itself if thats the part thats giving you trouble.