You can use a regular drill but it is recommended to also use a solder iron to prepare the holes to drill.
I followed
those instructions.
The gist of it:
1. Buy M2 screws (2mm) with a length of 8mm.
2. Prepare the barrels plate by making tiny holes with the solder iron tip. This help a lot to drill the holes.
3. Drill holes with a drill bit below 2mm (I think I used a 1/16", which is 1.58 mm).
The keyboard I repaired was not in mint condition: the barrels plate was horizontally split in two pieces.
Nevertheless, I'm currently typing on it and it works perfectly!