Sulley, that's the method I've always heard to use - scalding hot to near boiling water for several minutes. It makes the rubber pliable enough to stretch on or off the wheel. I once cheated and replaced a trike tire on a very hot Summer day by leaving it out in the sun for a few hours. It didn't soften it like the water would, but made it just soft enough to pry it onto the wheel without it splitting open. I tried putting a tire on the wheel cold, previous to that attempt, and it split completely open on me.
Dave