remove drum and remove all brake hardware - wash completely with degreaser and soap. NOT PETROL. let to dry, apply copper antisieze to the backing plate where the brake shoes rub, apply antisieze to the pivot pins too. Service the auto-adjuster and make sure its free, if you want to lubricate it use the antisieze on it too.
Use silicone grease on the slave cups and ensure their boots are good.