Hi,
Many use rotary tools for backround removal. Steve has a NSK at the airgraver site and also has some Video on Utube showing how it is used.
Others have put up threads on sharpening a dental drill for cutting out backround using a rotary tool
These are 350K RPM air turbines to do the job on metal. Mainly used in Dental Labs. These are not hobby type dremels or such.
Here is the tool Link on steve's site to learn more.
http://www.handengravetools.com/NSK_rotary.htm
Here is Steve's Engravers Techniques and Resources
http://www.engravingforum.com/showthread.php?t=419
All you have to do is check out this site and you will learn amazing things and get great help from Steve and Others on some of the best tools and see many of the members engravings and tutors.
Enjoy,
AirAmp