First you need 16 scrap metal(s), then fix all 3 leaks in Megaton so you can get exp from the guy in the water processing plant.

Then find the Outcast base called Fort Independence, start there (quest) to find tech for them.

Then take the scrap metal to the protector and give him all the scrap metal you have, then steal it all back (make sure he does not catch you).

Then give him all but 2 this time, then you need to steal it all back again without getting caught.

Then exit the pickpocket screen and pickpocket him again and get caught by trying at his laser pistol.

If you watch carefully in the top left hand corner of the screen it will say -14 scrap m and then it will say -16 scrap m.

OK, then go to the water plant guy in Megaton and ask if he wants scrap metal and choose 15 to sell over and over and over again until you have the level you want (you can't pick up any more scrap metal or it will stop the glitch).