I think that's completely different for everyone. For some, it could be a gradual process, for others a sudden enlightenment. For me, it's hacking away at the surface and trying not to feel too uneasy about the areas exposed. I try to make a constant effort to be 'true' about who I am and I let myself get hurt. I would never do something like that before; instead I'd partition off any feelings that needed to be dealt with or let the surface persona deal with them or find other ways to get around the whole emotional aspect. I'm not saying that it's typical, only that I've observed, heard and read about this in other ENFPs, but it might be something quite a few types experience.
Okay, how can I tell that I shed my skin - well, first of all I feel a lot more exposed. Everything is a lot more raw and a lot more meaningful. It's like the difference between wearing and not wearing glasses. Only, in this case, things get a lot sharper, nastier and more true to life when you wear them - which would be shedding the skin. The muffled, grainy world I get from pouring energy into my 'skin' lifts and everything becomes more clear. But I'm not sure if I'm phrasing this correctly, or if I'm projecting my own battles onto my type. I'd love to hear if anyone can identify with some aspect of this. It's not the same as having a public and a private face - this is something constant, a 'buffer-barrier' you'll even set up for yourself. It took me some years to even become fully aware of it and it still puzzles me.