I am not sure what the process that could be called "enlightenment" means.
If I understand correctly, you're asking what process in each thinker could be referred to as "enlightenment."
In Plato, the obvious candidate is the process of coming to discern the Forms or Ideas. The Forms seem to constitute a separate realm from the phenomenal world we experience, they show themselves roughly in the world about us, since what we see here are imperfect copies of the Ideas. For example, even though we may never have seen a perfect triangle, one whose inner angles add up to 180º, the rough approximations we do see suggest or remind us of the form of the triangle. I say "remind" because Plato thinks the soul's provenance is in the realm of Ideas, so that we have prior knowledge of it that is obscured when we fall into this world. In the Meno, he suggests that all knowledge is actually recollection--by ...