Nayashis [translator's note: lowering a note by 1/2 or 1 pitch, then raising it up to the original pitch] are often found in honkyoku. They seem simple, but it's hard to get them exactly right.
In honkyoku played at the Shakuhachi Kenshu-kan, nayashis on Ro, Tsu, Re,Chi, or Ri should fall a full pitch, while nayashis on Tsu-meri or U should fall a half pitch.
Once you have the pitch down (which is itself challenging - many people do not drop their nayashis far enough), the next challenge lies in speed. It's boring to have all your nayashis the same speed. There should be some like large, slow waves, and others like quick, small waves, all depending on the context of the phrase within the piece.
Try listening to professional recordings from the perspective of nayashi speed, and you may hear things you never heard before. Varying speed sounds easy, but in practice is quite difficult.
The same thing can be said of uchis [translator's note:"hitting" a hole]. Often multiple uchis will appear in the same phrase. This phrase, for example, is common: Hi I - - - Hi I - - Hi I - - Hi I - Hi
Each "-" shows how much time separates each note. The separation between each note gets smaller and smaller as the phrase progresses [See Aug/2002 for more detail on this subject].
Nayashis and uchis vary depending on their context within the piece and even within the phrase. There is no such thing as a "standard"nayashi or uchi, and being able to vary them at will depending on context is difficult to say the least.