Most of the methods for doing this seem to involve elaborate setups with landmines or cheating with console commands; this method works on my unmodified XBox with patches to date and needs no hackery, although it'll probably take you a few tries 'n dies to make it.
Here's a scribbled walkthrough.... and just for proof, a snap of all 37 bars laid out back at the Brotherhood of Steel bunker, which by the way is ideal player housing for the rest of the game, containing a functioning Sierra Madre vending machine. (You did win the complimentary voucher back at the casino, right?) This is also on my newly-relaunched personal blog, chrisworth.com. Enjoy!