Re: the purpose of suburi in aikido?
I'm sure you have read before how the purpose is to reach a point where the sword becomes merely an extension of you.
Therefore understanding this means the point to reach is where it feels no different to the feeling thet you have now of raising your arms.
So I am maybe questioning your view of what you have been doing rather than 'wrong' method firstly.
In other words as long as you see it as a foreign thing rather than part of you you will never reach that point.
Here's some advice from me. If you see your legs and arms as extensions from center then develope seeing the sword as an extension from center too.
Thus you have a verticle center line that you are lifting it up on and cutting down on. Meanwhile extending straight out from center is it's line of rest that it starts from and returns to.
Thus when you cut down and through you hold that extending line so that it bounces back to it's place of rest.
As for different methods of training to attain such then we were trained in continuous cutting until we could do no more. Then we were informed that only now or at that point could we start cutting and lifting it properly. Thus we were trained from the view that until we had no strength left then we couldn't learn the correct way.
I visited a class by Kanetsuka Sensei where he had students non stop cutting up down up down using big tuck tyres to hit. Thus he was 'teaching' them to get rid of their shoulders and to experience the 'bounce back' feeling at the same time. Quite creative.