It sounds like you have a good plan.
Whatever liquid flux you buy, don't buy acid flux. That will eat your
track over time. I can definitely recommend the liquid flux by H&N
mentioned in my website. I use the "gel" for soldering feeders to
rail by using a toothpick to get a drop. I use a q-tip and
the "liquid" for soldering the feeders to the buses. The stuff works