drilling through metal cp

[sman26]

Hello.

I am planning on modifying an original asteroids CP which is metal.  I plan to fill in the existing holes, except the volcano button holes with bondo filler and then cut new holes.  My question is, How do I cut the new holes for button, joystick, spinner and 3" trackball into the metal?  Does a Holesaw work for these holes and drill bits for the smaller holes?  Are there special attachments for the end of my drill or dremel?  I would like a nice clean circle for these holes...especially the 3" trackball hole which will be pretty obvious if it's not perfectly round.
Any ideas would be appreciated.  My other projects have been out of MDF which is easy to work with.

Thanks,
Shawn

[BobBorakovitz]

I ended up using a step-bit after drilling pilot holes.   But I used a donor piece of sheet metal, cut it to the proper size, covered it with some rubber trim and drilled through both layers of metal at the same time.  I did that so I could totally alter the original layout but still use the original metal control panel.