I can't speak from experience, but I'll try and answer as best as I can.
1) Since it's black and not a light color like white, I think you'll be fine as long as you wear nude underwear.
2) My best guess would be a fabric paint.
3) T-shirt bra (or if you're really paranoid of lines, you can use those adhesive petals to cover your nipples and go without a bra), and boyshorts or a thong.
4) You'll probably be fine. If you're worried about size, you can always try body shapers like Spanx.
What's this for? It's a wig.
What's it for? To disguise yourself from yourself.
So what's it going to be then, eh?
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