Help with setup timings after backthrow



I have been playing makoto for a while now and have a good amount of setups after backthrow. I have been in the lab and trying to get the timing to start whiffing normals/Hayate Cancels into air tsurugis for crossups. I have a very difficult time finding the right time to start pressing buttons. I have been plinking and it still seems like I am starting early. Any suggestions would be greatly appreciated!