Knowing how to open a can with the ancient implements Barney refers to was invaluable if you were beer-enabled in the 60's but had to improvise if the new-fangled technology of pull tabs failed, or injured you severly enough so opening another was a life threatening event. Yes, learning to poke the second smaller hole in the old tin metal was one of those rites of passage passed on from father to son, like tying bowlines, crossing over the bag to make the double play, and how to undo a bra strap effortlessly (well, 2 out of 3 ain't bad....).
Given that Dustin H was 30 at the time, I suspect he used the can opener on a pull-tab enabled can of Oly, just out of habit and or boredom whilst waiting his chance to see Ann B naked. Those were the pre-Cougar days too, so the fact that his paramour was only 6 years older would be 26 years older in those days. Times change and time changes.