Re: Speed in waza?
Yes. Static before nagare. Smooth not fast.
But having done nagare kotegaeshi in a seminar after my first 3 classes in aikido, I'm inclined to think that it allowed me to understand some of the mechanical motions of the technique that helped with my kihon application for a number of years.
However only after revisiting it again under kihon with full resistance do i understand kotegaeshi even more.
So in essence. Slow, fast then slow again. Increasing resistance and danger to progress. Over the course of your lifetime I would think.