Has anyone ever done this?

Let's say you have a character (Sydney G2, for clarity). You have a scene where she is running away from something and wearing a simple hospital gown that you modeled in less than 5 minutes.

But you also have a second skin costume that she will transform into at a certain point in this animation, and the hospital gown will fall off her.

I got the gown to fall off her using the cloth room and a lot of tweaking.

But how do I animate her second skin to appear on her body a couple frames before the gown comes off? I will hide this transition with post FX, and the only solution I could come up with is that I would have to apply the second skin costume and then render several frames with it in place. This takes forever because I am not just doing preview render, I am using Superfly.

Any suggestions on the setup? I know it involves clicking the affected tabs to animate and using the Frame node, but I don't have a clue how to set it up.

If I had a nickle for ever time a woman told me to get lost, I could buy Manhattan.