I have finally figured out how to brew this tea! Correct temperature = 75F; steep time = 2 minutes. But the most important part of all is to use the correct filter, which I have determined through trial and error is a metal mesh cone coffee filter basket. I don’t like the result when I use that sort of filter to prepare coffee—it leaves too much silt behind, creating more of a Turkish style brew. However, the mesh size turns out to be perfect for removing the broken particles from brewed sencha, of which there are many in this two leaves and a bud sencha.
Using a more effective filter device to catch all of the smaller pieces of tea produces a much better first infusion! I always liked the subsequent infusions, but before I was finding the first one too bitter. Not anymore!