I spent way over half of my twenty year plus martial journey in the search of technique until I finally realised I had been barking up the wrong tree. And few thought to advise me otherwise. The name of the art is Aikido and, if you think a little, it is aiki that needs to be isolated, defined, sought after, and trained. To do this we specifically have kokyu-ho and kokyu nage and after years of doing it we ought to have a measure of aiki strength, or kokyu-ryoku. Of course, many do have more than a measure of such strength, yet, it is often more accidental than purposefully striven for. Somehow, in English, the word strength offends the Aikidoka, but there it is, in stark reality, in Japanese - ryoku. At the heart of the problem, however, is just what that strength is in realistic teacher-to-student transmission terms. We are always told to off-balance, to make good technique, to practice smoothly, to relax, to remove tension, to find an easier way to do it all, all the while without explaining the how of it - as though some magical means is supposed to just one day reveal itself. This cannot be right. Part of the problem is in training methods and names, or rather, the lack of them. If you come across something interesting in Aikido, there is likely no name for it thus no means to isolate and quantify it, or worse, remember it.
In Aikido, the system is such that if you find a teacher who can do things to you, as uke, it is your responsibility to learn and remember with little or no useful explanation. Such is often your total 'direct' experience yet in fact it is quite secondary or rather, 'indirect'. It can only become direct when you try to do what your teacher did back on him, or on others. And it only becomes direct if you get it right. If you cannot get it right, it cannot count as direct experience in any way whatsoever. Accordingly, if you have an inkling of it, it is your task to chase it, to develop it, and to rediscover it. And if you have it, it is your responsibility to come up with the means to pass it on. I say 'come up with' because there are no widely recognised or named means.
I will contribute a couple of 'names' to the discussion:
The wheel: Imagine a car wheel solidly fixed on top of a rigid pole such that it rotates horizontally. If you push or hit it anywhere but the centre, it turns and deflects your hit. The wheel turns but the pole in the centre does not move. The aim, here, as uke, is to hit the wheel dead centre such that it receives the full force of the attack and does not move at all. This creates good centre in uke that ought to translate over when in the role of tori. The aim, as tori (the wheel), is to try to deflect that which uke does not wish deflected and the one with the strongest intention/centre wins. This is, at heart, the strength of Aikido. Thus our training should be such that we have as a major aim the idea to develop a strong intention/centre. That being said, faced with the slightest lateral movement, the wheel does not resist at all and simply turns. So, make yourself like a wheel: Focus straight ahead strongly - like the axle - but be completely free to turn - like the wheel.
The ball: If you press on a ball on the floor, the ball presses back and resumes its shape once you let go. Newton would agree that this is quite a natural phenomenon. Thus, if you press uke down and release the pressure, uke should get up - if the attacking spirit is genuine uke will get up naturally, if not genuine, uke thinks 'I am supposed to get up now,' and gets up, but is quite late. The genuine attacking spirit in uke might also be likened to pushing a ball under water - if you do not focus dead centre, the ball slips sideways and pops up instantly, or if you like, honestly.
A similar phenomenon occurs when pressing a ball against a wall - the ball pushes back to regain its shape. If you press against uke slightly, they will respond almost without knowing it and you can lead this instantaneous involuntary response to dissipate the strength of their attack (strong grip) and take their balance. You cannot do this in a one-two fashion - this instantaneous reaction must be used to lead their balance and make technique in the same instantaneous time. With practice, the same pressing-the-ball idea can be used in the midst of, or better, throughout a technique. You can press softly or firmly.
Aiki-strength
While the objective always seems to be to do everything gently, I assert that pressing strongly allows a better development of the principle and thus we should seek to find grace from within developed strength. Accordingly, the strength of aiki, or should I say, kokyu-ryoku, demonstrated here is directly proportional to how hard you can say, press and rub a ball against a wall while keeping balance and posture. Thus, you need to train to make it stronger, stronger, stronger, not weaker, as is often heard. And remember - the aiki strength here I keep referring to is not standard muscular strength, but kokyu-ryoku. Also, pressing is not pushing.
It might seem that the wheel belongs in the attack section and the ball in the ukemi section, or even vice-versa. That may be, but in order to train with an aiki purpose, all have to be ultimately brought together under the roof of aiki.