Wetzell's flash card method included tactics and positional ideas that he missed in his own play as well as those he missed when playing over one side of master games (using a clock) and trying to guess the next move. His idea was that by concentrating on those positions where he missed something important he could build a mental database of patterns he would recognize the next time they appeared. This is really another method of note taking and studies conclude that good note taking improves the learning and retention. See the post on Chess Notebooks.
In this game I mention that the win would require technique. What, exactly, is technique and how do you acquire it? According to Frank Marshall the hardest thing to do is to win a won game. It often requires technique, the ability to convert an advantage into a full point. As GM Daniel Naroditsky stated, simply sitting on a position and squeezing the life out of your opponent is sometimes not enough; even if you have outplayed your opponent positionally you must often switch to concrete calculations that involve tactics to finish them off. I guess knowing when and how to that also could be considered “technique” because it also comes under the heading of knowing how to win a won game. So, how do you get technique? I have no idea.
The following game is filled with a lot of tactics, most of which Wetzell either missed or didn't comment on in his book. And, it also shows that even masters can make a lot of mistakes. I believe that his opponent in this game was rated somewhere near Expert (2000) strength at the time this game was played and, as should be no surprise, it was insufficient tactical skills that prevented him from taking advantage of the opportunities the master presented him.
The lesson to be learned is that in addition to endgame knowledge, we all need to hone our technique, positional skills and tactical ability. Not to discourage anybody, but even after reaching the coveted 2200 mark, you will still be a long way from being anywhere near as good as a Grandmaster. Just see my anecdote about Quniteros at the end of THIS post.