Re: spiral form
Your hand would make a spiral, but what is happening to uke at the same time? By attacking you, uke is putting his force forward. You are hitting it perpendicular to his force, so he is real weak.
Since we all have only 2 feet, there is always a weak point in our stance. No matter how stable we think we are. One weak point is perpendicular to your feet. It's always there no matter how stable you think you are. Try doing a spiral type technique and pay attention to when you break uke's balance.
You have to go very very slow to really see what's going on. You will note that every time uke's balance is broken perpendicular to his feet, he has to adjust himself to keep in balance. Once he regains it, he will get hit perpendicular to his feet again, and again and again.
This happens over and over creating what looks like a spiral. Eventually his structure can't stay in balance anymore and he will fall.
If your timing is off, and you push through this point, you will actually put uke back in balance.
I hope I am explaining this so you can understand it. It's a lot easier to show.