I just thought of something. Perhaps for some of us, the two things happen simultaneously. The shingles drop from our eyes, and we change...also we change, and the shingles drop from our eyes. Right now, this is the only way I know to say this. If it happened too rapidly, as in the case of Paul (Saul), some of us could not handle or contain it, so for some of us it happens slow, as we are able to take it.
You have described it well. This is, actually, a concept within Hindu understanding of how we come to realize the Truth. :) Our spiritual practice, our life experiences, these may be said to be preparation. We must make ourselves ready, step by step.