I have practiced the defense from Sochin for a while. Attacking the hypoglossal nerve makes this more effective, and I finish by dropping their head into a rising knee.

However, I find the application from Seiunchin difficult to perform. What could I be doing wrong?

I have heard Sochin "Grand Suppression" and Seiunchin "Blue Cloud Battle" are paired kata. Is this true? How come one is a Shuidi and one a Nafadi kata?