I lived in Miami for 10 yrs and had to learn how to deal with fire aunts. Best remedy I found was finding their nests and poured 3 or 4 gallons of scalding boiling hot water right on top of the nest. It proved a determent.
Sounds like a good method. I think every inch of my yard has ants. I put spectracide on the mound then pour cold water until the mound flattens out, and that does destroy that location, but then they pop up nearby somewhere. Next time I will try boiling water LOL