Or also, have you cleaned and greased the 6 contact spots on the backing plates where the brake shoes ride? They need to be cleaned and a light coat of axle grease on the 6 flat spots on the backing plates so the shoes move freely.
I would suggest using brake caliper pin grease if some is readily available, rather than axle grease. Either way, put just a minimal amount on the 6 spots; don't slather it on.
