It may be a more tricky task than it appears, since to
degauss the object one has to apply exactly?

Degaussers work from line power by generating a strong 60 Hz
alternating flux which is slowly decreased in intensity by removing the
degausser coil away from the subject. I'd remove the compass and any
electronics first though for that reason.

I'd think a strong or larger degausser could be temporarily made from a
500 ft coil of three conductor (plus ground) # 14 romex wiring cable.
The ends should be connected to make a 2000 ft coil, and the whole mess
tied together with tie wraps. As an alternate the whole mess could be
made with 3 conductor extension cords. & a suicide plug/socket
arrangement.

Has anyone ever tried something like this?

Neil