You make me laugh! Yes, "The Insulator" defeats his foes by wrapping them in fiberglass insulation, then cocooning them with 4 mil plastic wrap with a Tyvek bow. They don't stop itching for weeks!
As you asked about VB's (vapor barriers, but I like the acronym) the seams should be applied vertically on the walls and horizontally on the ground. (hee hee. ask me another one, these are easy!)
It ain't easy to install VB under a house, but this is how I do it. Take the roll and roll out about 5 or 6 feet of it butted up to the near wall, running the lengthwise direction of the house, parallel to any crawlspace rows of posts or stubwalls. Lay on that part of the roll and work your way up to the other end of the house. When you get it unrolled the length of the house, cut it off from the roll, and start opening it up to its full 10-12 foot width, working your way back to the starting point. (bring the roll back with you as you go.) This might be easier with a helper, but I don't play well with others so I have never had the pleasure of trying it.
Ask a more specific question as to the "how" part, and I'm sure The Insulator will find a way to break away from crimefighting to answer it.