Just want to add that the pH you're shooting for (5.2-5.4 at room temp) is for mashing purposes, to get a more efficient mash. You asked about adding baking soda to your boiling wort - but by this point, we don't care about the pH (relatively speaking). The only salts you should be adding to the boil are for taste purposes (left-overs from the mash - that is, salts you wish to add for taste but that would have driven the pH of the mash too low if you would have added them). The purpose of adding baking soda as mentioned is to drive up a low mash pH. If the mash is done, then there is no need to add baking soda for these purposes.
For example, when I make my recipe I decide what I want the salt concentrations to be (approximately), and then I plug all that into a water calculator (you mentioned Bru'n, I prefer Brewer's Friend). I first add all my salt additions to the "Mash" section to see how it will affect my pH. If it's too low, I move portions of the salts to the "Boil" section (this way they don't go into the mash and thus don't affect pH). If I've moved all salt additions to the boil (none in the mash) and the mash pH is still low, that's the only time I'd add baking soda to the mash.
If my mash pH was OK, there would be no need for baking soda and thus you wouldn't add any to the boil.
I usually go with pickling lime to raise pH. Just be sure to add it after dough in.
