as with most things in life you need a bfh ....big sort of hammer. beat the blazes out of it then run a grinder round the inside of the drum, there will usually be a ring of rust and rubbish round the inside of the drum where the shoe does not wear , if that makes sense, this is the bit you want to grind off, leaving a few mm of a taper around the drum interior. that ring causes binding with drum going round and also taking it off the axel, get rid of that and a bit of adjustment on the shoes should sort you out....make sure your adjusters are working properly and drums are centered.
they can be a bit of a bugger if the adjusters are not holding properly, make sure they are locking it place as well as adjusting.