Well if you're tool is either too weak or powerful, I guess you would need to resort to muscles
heh!... I'm playing around.... but there is some truth there.
I use the wrong tool for the wrong job on a regular basis, but what fstfrddy stated is a basic rule for success.
My little Dremel gets a great workout, but it has yet to fail me.
Back to the original question: For cutting on metals or alloys, a Dremel or Roto-zip are not ideal. If you could get a holesaw (expensive) and a 1/2" drill (preferable, but most corded models will do and even some newer cordless models), you will be well on your way to success.