So between the deck going in and the pebble install, I got a bunch of dust on the stone coping that doesn't want to come off with a pressure wash. I did a little research and got some ideas but wanted to throw it up here for a sanity check before pulling the trigger. So my thought was to mix 1 part M Acid with 2 parts water. Then wet everything down so I don't etch the concrete in case I get a little over zealous. From there just use a sponge and wipe it on until the dust dissolves.
Does this sound about right? Am I missing anything?
P.S. here's what it looks like now...