One tool:
A Dremel, will do this.
Just have a test on a bit of the same material before you start chopping into your panel face.
Punches are OK, if you like the expense of having something you may never use again.
If you don't mind a bit of filing to make the edges a bit more "friendly", the Dremel is the way to go.
One tool I have had for years is what is known as a "Die Grinder" it holds smaller type bits like small grinding bits and also flap-discs.
It is a lot higher powered than a Dremel and uses lower speeds.
I've always found the flap discs great for cleaning up cut out holes in a jiffy and it makes a nice smooth edge to the finished hole.
Coming from an engineering background, I'd recommend you get some of the film that 3M sells, that is used on stainless steel sheets during transit to save any knocks to the finished product from the factory.
It is adhesive and is black on the sticky side and white on the outer side.
I usually do my marking out on this with a mechanical pencil,once the film is in place, you could also do this with a very fine tipped Sharpie pen.
Having said that, I have also cut out reasonably "round" holes with a small angle grinder (always smaller than the final hole size), with a cut-off disc and got them within a ball-park of finishing them off with a die-grinder.
Just bear in mind that when you are grinding away, the hole is getting bigger and never let a grinder of any sort "dwell" on any point of the cut out.
Constantly check your work, it's rather hard to fix up something AFTER you've mucked something up.
