> Is non-dualism something you experience in a flash then use as perspective in everyday duality life?
*****
It's something you already know, only perhaps you haven't noticed the knowing of it, yet. The first knowing of it might come as a flash, like when you see a very well-camouflaged moth on similarly-colored tree bark. Once you've seen that moth, you'll find it harder to miss on subsequent viewings. Nondual truth can be similar to that. After the flash of the first recognition, you won't mistake it again and it becomes an ongoing revelation of your true nature.

> a state you visit regularly?
*****
It's a state you've never not been in. The recognition brings a direct, ongoing awareness of it, but the actual truth of our nondual selves is with us always, whether or not we know it directly.

> do some people actually spend their days walking around at one with everything?
*****
We all do, all the time, whether that initial recognition has occurred or not.

The recognition brings a new, constant state of awareness of our nondual nature, yet the world remains the world and we remain the nominal individuals we've always appeared to be. Some gurus may try to con us into believing that they've lost all sense of individual self, or that they walk around being everything, all the time. But if they answer to their name, you've caught them in their fib.

By grace our Nature (non-dual) reveals itself to us, usually starting with a glimpse that is more like being seen than seeing something. Our mind/brain system cannot hang onto this glimpse, just as on awakening from deep sleep you cannot say anything except that there was a deep sleep.

It is not a perspective that can be used. That which is non-dual has no perspective. Perspective is a condition of duality. Though we can "practice" living and perceiving from a non-dual perspective until it awakens in us.

Yes, but the question of someone walking around at one with everything can only arise in duality, from non-duality there is no one and no everything to be at one with. Duality itself isn't separate from non-dual, all pairs of opposites vanish. It is why it is called non-dual, because the only things that can be said about it are what it is not. All language engages in concepts and perspective, language can only point toward the non-dual, never reveal it.

ohm