very few moving parts. they're real easy to work on. no special tools, way easier than a car's drum.
as far as rubbing goes, if it's just a slight drag, that's pretty much par for the course for drum brakes'especially if they're pretty new. on a bicycle, it takes months to break them in so the pads seat.
every drum brake i've ever had, they get better with usage. worksman, and especially sturmey archer, don't work that great when new.
one trick i've learned is to "drag" the brake when you're cruising around. just lightly ride the lever on a nice long straight for awhile. it speeds the seating process. don't worry about overheating it or wearing it out.even on hard, everyday usage, they' ll last a lifetime.
i've got an atom drum from the 60's i've used for almost 3 years and you can barely see any signs of wear. i have to adjust the barrel about every 2 months, and just by a little bit.
i adjust mine by spinning the wheel and get a tiny bit of drag, then back the cable adjuster off a hair, pretty much like a car.