Who are the people that know how to use Kaio-Ken?


Are Kakaroto (Goku) and [Kaiō-sama](http://dragonball.wikia.com/wiki/King_Kai)
(King Kai) the only people that know how to use the Kaio-Ken?

Did Kaiō-sama teach his technique for others beside Goku? For example, while
training Krillin and the others.




King Kai himself was not able to use that technique, and he said that Goku was
the first one who ever mastered that technique. However, King Kai tries to
teach the technique to everyone who visits his planet.




King Kai himself was not able to use that technique, and he said that Goku was
the first one who ever mastered that technique. However, King Kai tries to
teach the technique to everyone who visits his planet.

