I got a mesh bag but I never use it (it's now my regular laundry bag), as I prefer to go through the nappies individually before washing to double check that velcro tabs are done up and there aren't any stains that need the Vanish treatment first.
I usually pour a kettle of boiling water into the bucket to clean it, sometimes I add a squirt of bleach or some Dettol spray, or a few drops of lavender oil.