I wasn't able to use Dwarf Companion, so I'll give you an easy step-by-step.
1. Set up standard fortress at beginning.
2. Export very little. 50 dwarfbucks did it for me. Less export means less immigrants. (you want to hit just 20 dwarves.)
3. Have any dwarf without a mood skill (
http://www.dwarffortresswiki.net/index.php/Mood#Skills_and_workshops the ones in the middle don't count) make ONE weapon. Switch the weaponsmithing jobs on and off assuring that all dwarves who would normally make an artifact craft, have dabbling weaponsmith.
4. Once you have 20 dwarves, set up your sheriff, then save!
5. Soon after that, a dwarf will befall a fey mood. If it's one of the ones whose highest mood skill is weaponsmith, then let him go to work. If not, ctrl alt del to terminate without saving. Do so until a weaponsmith gets a mood.
6. save while he makes the weapon. ctrl alt del until you get the specific weapon you want. (It's picked at random while he makes it)
7. Make sure said weapon ends up in a bin, and know that it will NEVER leave that bin. Weigh the bin down.
8. Find bin in Adventure mode, and get artifact weapon!
Notes:
a. whatever material you want it to be, make a stockpile for that type of bar next to the forge. They seem to automatically pick the best bars.
b. In adventure mode, if you drop or throw the weapon when you have it, it will disappear. Don't freak. It can be found again in exactly the same bin. (It never leaves, you just take copies of it. You can't have more than one outside the bin, though)