Hi
I just had an MOT fail due to rear brake and handbrake efficiency 15%!
The drums are fine as are the shoes.
Replaced wheel cylinders - luckily because one bleeder was broken off.
Many of the pins and shoe retainers rusted completely away.
The handbrake lever attached to the rear shoe was rusted and very hard to pivot as it should. Cable attaches to this.
This resulted in brakes dragging ( not releasing).
Also the cylinders probably leaking or about to as there was fluid under the dust caps.
The fix cost about £25 being -
new wheel cylinders about £6 each ( on special at Euro's) normally 11-12 ish. Its not worth trying to just fit new rubbers.
Shoe mounting kit (GSF) £12 ish.
Also had to have a new brake pipe from flexi to wheel cylinder - because previous mech hadn't bothered to use brake grease on the nut threads and bleeder threads!
Few hours on cleaning and refitting it all and a little pre-adjusting to give the self adjuster a chance to fine tune the adjustment.
... and job done - MOT pass and good braking again, including handbrake!!

all for about $25-30.
Plus a bit of brake cleaner and copper slip and brake grease. Don't forget the caps on the bleeders when you finish!
Not technically difficult just a bit dirty and tiresome - just make a sketch or have a manual handy for the springs and clips whereabouts.
After doing mine IMHO it would be better to overhaul at the wheels first before spending on cables etc. They may be needed later but problems at the wheels more likely.
Jon