Originally Posted by Vagrant Lustoid 2

You do not need to. Did you miss what I said before about how the Kai pointed out that Goku had already been using KKx10, and yet it hadn't been shown? Clearly, it's an instantaneous flicker of power for a brief moment, so fast that the human eye doesn't register it.

And that's pretty much how they describe it, as a really brief flare of power.