For modest interference fits, force and heat can work.
Producing a large enough temperature gradient usually requires that the heat be applied rapidly, by a serious heat source, like a flame.
If the interference is substantial, it becomes more difficult to salvage both parts. If one is to be replaced anyway, it may be better to destroy it to save the other.
Easiest way is to give the assembly to an experienced mechanic and go out for coffee. You may not want to watch his process.
Mike Halloran
Pembroke Pines, FL, USA