A few things not in the article:
1) When changing the upper tension dial, the presser foot must be lowered to engage the tension.
2) When making a sewing test, it is best to use the same thread in the upper and bobbin, including the same color. Believe it or not, dye content can affect the tension. I would never have thought that, but Ray White made a believer out of me.
3) To test for balanced stitches, sew the best seam you can get on the straight or cross grain. When you think you have it, make the same seam on a double layer on the bias. Holding both ends of the seam, pull and try to break the thread. If both or neither of the threads break, your seam is balanced. If the top thread breaks, loosen the top tension. If the bobbin thread breaks, tighten the top tension.
4) It is possible to have a balanced tension and still have the tension too tight or too loose.
5) If you are using different threads, for example bobbin thread in the bobbin and quilting thread in the top, repeat the test. My experience has been that when using this combination, I need a much lower top tension than when both threads are the same. Your mileage may vary.