data security

It has been said the standard industry practice is to reformat and rewrite the disk four times, and then degauss it. This method provides the greatest assurance that any data that was once on the hard drive is either removed or unrecoverable.
First question is how do you degauss a harddrive and second is there an afordable software ($15-$50) that will preform this writ-over automatically via external USB HHD enclousers?