One of the first things I noticed when I started swimming with DragSox (aside from how hard I had to kick to keep moving forward) is that DragSox forced me to develop better rhythm and timing. Because DragSox add resistance, any dead spots in my stroke were quickly exposed. Every time I had a dead spot, I felt like I stopped moving forward and had to work much harder to accelerate to gain speed again. This slowing down and accelerating wastes a lot of energy. I took it as an indicator that I needed to work on my rhythm to make my stroke smoother and more efficient.
The "Dead-Spot" challenge: identifying inefficiencies and improving your rhythm and technique:
Try swimming a couple of 50s with DragSox at moderate speed. Pay very close attention to the way you move through the water. Since DragSox slow everything down, you have more time to feel every movement of the stroke. If at some point you feel like something is "wrong" or every once in a while you feel like you slow down and then speed up, chances are that it's a dead spot in your stroke. Maybe you try to glide, or you're out of balance. Then take DragSox off and swim a couple of 50s at the same pace and pay close attention to the parts of your stroke that felt "wrong" when you swam with DragSox. Usually, if you repeat this exercise enough times, you'll be able to narrow down the exact problem. Then you can start to fix these "dead spots," improving your rhythm and technique. It might take some time, but eventually your stroke will become smoother and more efficient.