There's a few things you can try. One thing that may be holding it up is rust on the hub itself, rather than the shoes grabbing a ridge. Try rapping the drum between the studs to loosen it up. You may have to get behind the drum with a prybar to apply pressure while rapping the drum with a hammer. A brass hammer is preferred for this, as it is far less damaging to the drum. Once it seems to move, try prying 180 degrees out to "walk" the drum off. I've used this method many times, especially on vehicles that have no provision for backing the adjuster off. It will take a little time to do to prevent damaging things, but it does work.
