Popping
In many (all?) cases, the realization of no "I" seems to pop. There is a sudden shift, no "I" is clearly realized, and the "ground" all phenomena arises from and as also pops into the foreground. It just seems to happen, often following a longer period of certain practices.
This is similar to the phase transitions of systems theories, where the system suddenly shifts from one attractor state to another, often with a phase of instability in between - where the old falls apart and the new has not yet appeared.
And it is also similar to the popping of gestalts as described in gestalt psychology. First, we cannot make anything out - we may be told what to look for but cannot see it even if it is right in front of our eyes. There is a focused effort here, but for a while it seems to yield little or no results. Then suddenly the image pops out, it is obvious, clear, beyond any need for effort or strain.
Nothing has changed, yet everything has changed. And what appeared to take a lot of effort is now there effortlessly, on its own.