The trick is moving it in a circle near (but not touching) the picture tube. You want to remove the magnetic field the tube developed.
A real degauser looks like a ring - about 1 foot in diameter, and it's wound with wire:
http://www.datadev.com/dc13.html
All you're doing is creating a larger magnetic field nearby the picture tube which strips the magnetic field from it.
Most modern monitors have a built in degauser which is just a metal ring wrapped around the outside front edge of the tube and wrapped in wire.
A soldering gun and bulk eraser are nothing more than big electro magnets and, while not ideal (a degauser ring works better) can be used as a degauser.
A bulk erase does the same thing essentially - strips the magnetic field from a tape.
A soldering gun is basically a big transformer which also - as a side effect - produces a large magnetic field.