Slow makes fast
I believe that slow training is the way to learn how to do things fast. In really slow training, even the minutest details are polished, and your body gets very well acquainted with the technique.
It is also a good way of discovering weak spots or moments in the technique. When you do it fast, you easily just rush past weaknesses.
That is true for every aikido technique. Also in the sword arts. Try to do basic suburi exercises very slowly, and you will discover weaknesses that you were not aware of when doing them in normal speed.
A friend of mine trained karatedo almost only in slow-motion. Even the high kicks, such as jodan mawashigeri. After some time of such training, he was able to do the techniques extremely fast, without losing the least of their precision.
Indeed, slow is the way to fast.