Actually I hadn't heard that exact method but I may not have thoroughly read the web page that I was reading. (Something about using a tiny sewing needle to drill the hole with a pin vise. I remember sanding but not dimpling, just drilling the hole with the needle.)

I went out and bought some goodies this afternoon including an assortment box of sewing needles and a Dremel tool. As an experiment I put the thinnest, sharpest sewing needle in the dremel's chuck, turned it on at 20,000rpm, and without any sort of modification it did a really nice job of drilling some really nice round (aside from the burrs) holes of various sizes in a soda can I tried it on. I also ordered this thing online that is basically a drill press sort of holder for dremel tools, so perhaps I'll see what I can do using that and various grinding bits.

Using a Dremel drill-press-style might be overdoing things a bit but I keep running into other stuff that I need a dremel type tool for, so I might as well see what I can do with it for pinholes since I have the thing now.

I also have these old metal Polaroid pack film cartridges that I seem to end up with every time I buy an old Polaroid or Polaroid film back. They have some nice flat sheets of metal in them behind where the negative goes, but they're kind of thick. (Double or more the thickness of soda can aluminum.) Extra thickness might not hurt though if I try to use dremel tool since it ought to cause any sort of drilling or grinding to go more slowly and thus carefully. Not sure what metal they used for these old cartridges though.