I have used the can opener that comes from Russia, but I have found that a hammer with a 3/4" and a 2" wide cold chisel is much easier and faster.
You use the 3/4 chisel to go around the corners. Use it like a shear, starting with a corner and advancing the chisel at about a 60 degree angle.
I can take the top off a Russian can in about 20 seconds with these tools
Try them; you'll like them better than the can-opener.