deckboards, no powerwashing needed. just make sure there's no caked on
mud or bird mess, etc. you know, the usual stuff. for the railings, it
depends. how long has it been since you stained them? have they
weathered? that's usually what the powerwasher is for, stripping away
the gray weathering. just keep a steady hand so the new stain doesn't
look splotchy.