Help Grey Fuzz!!

I have a rough sawn white cedar tongue and groove paneled wall on my covered deck. I used olympic premium deck cleaner and I hate to admit it but left it on for 1.5 hours but the directions called for 5-10 minutes. Also lightly pressure washed the wall.

Needless to say it is really messed up. White stripes on the wall, serious amounts of grey residue that does not come off with pressure washer. Even sanding in a test spot does not work well, due to the unevenness of the boards. It takes a LOT of sanding to get it all smooth.

Is there anything I can do short of sanding the whole wall??