Maybe you know already, but before you do all that banging you should put the nut back on the end of the axil (backwards) so as not to mushroom the end of the axil. And if you have the emergency brake on during the banging procedure then you'll be helping to keep the drum on. If the spinning drum is a problem then you can stabilize the drum with a piece of angle iron situated kind of between the lug bolts and against the floor. One time (on a really stubborn pair of drums) I used angle iron and drilled holes (2)in it so I could bolt it onto the drum with the lug nuts and then prop it against the floor. It keeps from having to resituate the iron after every bang.
As for the banging itself. Sharp, forceful bangs with a medium or larger sledgehammer seems to be effective. See if you can retract the brake pads before starting. Otherwise, they will be assisting in keeping the drum on. This is especially true if they have not worn evenly, which they probably have not.
I'm not sure about using the heat. I've taken drums off more than a dozen times and have never used it. BP Blaster or some other rust breaker may help.
I'm always surprised at how hard they have to be hit to get them off.