PeterR

For me it has always been a matter of rhythm and feel. At speed it is always (for me at least) to maintain that. Slowing the practice down runs the danger of degenerating the technique into a series of discrete moves. I guess that is the same thing as the "Slow and smooth, smooth and fast." but I just want to stress that you need to look and perform the technique (no matter what the speed) as a whole.

It is also very important to have a partner who understands what you are trying to work on. The dynamic of uke often changes with the speed of practice to the point where it can be worthwhile to do the slow exercises solo.