I agree that nothing changes, except for what we are experiencing. Most of the time we experience thoughts. When we sleep we experience dreams. This is as things have always been.

We can experience a state of no thought. A state where there can be no naming. In non-rem sleep the cortex has been found to no longer be able to integrate information. Thus a state of no thought.

Cortical bistability, as reflected in the loss of phase-locking to a stimulus, leads to a breakdown in the ability of the cortex to integrate information https://www.nature.com/articles/srep30932

This state occurs already in our bodies, just usually in deep sleep. When we meditate with the frame of mind outlined in the post, I believe that our brain will enter a state analogous to deep sleep states. This occurs after being without physical or mental movement for an extended period of time, while maintaining the meditative posture.

So we are unveiling a brain state that already arises naturally under certain conditions. Usually we are uncounscious/deep sleep. Meditation allows this to occur while conscious and alert. I believe no gradual training is necessary as gradual training involves 'exercises' which are geared towards altering the behavior of our cortex/thinking mind. Since this experience is outside of the realm of the cortex, anything we do to alter the cortex is irrelevant to the experience of a nondualist or 'no thought' state of being.