Kuji kiri are more to be used as mudra than anything else, hand configurations that you use during meditative exercises. Some of the more advanced forms however require manipulation of meridian lines and acupuncture points to my knowledge, and shouldn't be performed unless extensively schooled.
Also interesting of note: supposedly Krabi Krabong had meditative exercises with mudra too, meaning all the Muay Thai guys that diss it really ought to stop and think because they're also trashing on their own tradition
