After ruining several, I've come up with a technique that seems to work.
1. cover affected area with masking tape on both sides (easier to mark and the bit doesn't slip)
2. mark and dimple the center of the hole with a nail or punch
3. drill small hole (1/4" or less) The smaller the hole, the less tendency to tear out the flimsy metal
4. use conical "burr" bit to expand small hole to desired size--essentially filing away the metal all the way around
5. for multiple holes of same size, put tape around the cone bit partway up from the tip so you hit the tape just as the hole gets big enough
I don't bother
I use a no cut method leaving a sound hole beside the neck. This works best on square tins and not so good on round ones.
See how I do it in this instructable.
The best way to make a hole is to use a Chassis punch, but they're not cheap.
A step drill does a great job on sheet metal... HF has a pair up to 1-5/8"
HF also has a knockout punch set that should work. $25... several sizes up to 1-1/4
bullet holes would look cool...
Haven't used a chassis punch since aluminum chassis caught on in the 1950s. Wondered where I could get one. The HF knockout punch looks like a similar arrangement. Gotta' give 'em a visit...
I like your idea to use the melamine chopstick for the nut.
you'll need support for cutting sound holes.
I put a piece of wood underneath where I'm about to drill or cut a hole.
never had a problem using this method.
I back the can with a wood block and pound a nail through. Without any backing I use a step drill to drill it out to the size I want. The drill rounds the sharp edges down into the can. Most of the time I put the holes on the sides of the can so it won't mess up the nice picture on the top.