A goodly part of the reason for using that technique on labware was that it also sterilized it to a greater extent, which was often an important factor before their reuse.
As for using it to dry out your boiler, I'd say .... Good Idea! It is also used as an additive to absorb the water in fuel tanks and render it "burnable", which is slightly different that aiding in its evaporation ..... but not really much different, as it is in general making it more volatile either way!
Living in a hyper-dry climate myself, I simply leave the whistle and safety valve off of boilers that I put away in storage, and the little left behind by the syringe takes care of itself in short order, especially if emptied hot, which I always strive to do. If living in a damp climate, or at least on a damp day, my typical technique would likely not be a good way to go, which is where alcohol could come in very handy!!!