Ok, I tested this the other morning and I got it to work. For my Weller soldering gun, the critical part is passing the graver through the narrow end of the tip and not through the wide part (which did not work for me).
My advice is to get a demagnetizer but this can work in a pinch.
just wait-- you'll burn yer fingers if you do this often. they are easy to make for those of you that tinker. all you need is a small transformer coil. wire a common lightbulb and on/off switch in series, you're good to go. all the eletrical connections should be covered to prevent shock. the lightbulb is needed to protect the coil from burning up.