We really hit it this week with the soda bread.
I just toasted a day-old Irish soda bread I reserved for myself, schmeared with butter.
I got the right combo of sugar (3 parts brown sugar to 1 part white sugar).
It helped to put in a hotter oven -- got a good rise -- 425 degrees. After the bread rises and begins to brown, temp lowered to 350 degrees to finish.
When the dough is mixed, you want to knead/handle it as little as possible -- this makes for a soft, feathery crumb. Our crumb this week was good, if a little dense. Figuring out the correct hydration (buttermilk) ratio will help with this (the past two times I have baked it, I have had to add a little extra flour, then mix a little more to incorporate -- that extra mixing time toughens the crumb).