You can chip and blast and spray and lever on the shoes, just don't damage backing plate or drums. Everything inside is replaceable cheaply. Taking off/loosening WC is a good tip. As Tim says, get some shoe showing so as to knock it inward or break lining off. Hard to damage drums. Bang hard all around drums with rubber or dead blow hammer. Over and over and over. Does not matter what you spay in there if it works. (Nothing that swells lining, of course)

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn