When the Buddhas and ancestors of the past achieved realization they saw that their own mind was Buddha. All that was necessary was to drop the concepts of what mind was and to look at  mind itself.
They saw:
That there was nothing outside it.
That there was no separation in or from it.
That words and ideas obscured it.
That they were perfect and complete as they were.
That there was nothing further to seek.
Of course this is true of all of us as well.
So we do not practice to become Buddha.
We practice because we are Buddha.