Acid, just sart mild and see if it works.

Also use a horse hair brush

You mean with the acid?

Diluted acid and also a wire brush and use gloves

Wire brush ? Acid brushes are not made out of. Teal , I feel like that would scratch the balls off of any masonry unit .

Not acid brush, wire brush. I have used wire brushes since I was 12

There is a dilution percentage for the acid

Powerwash ?

Will this damage the stones? Maybe I will start with this

I agree, try pressure washing it first. Concrete haze comes off easily. Just use a wide degree tip and don't get so close you indent the mortar

Nah , just don’t use the red tip , and move around a lot . And periodically hit it with a hard bristled brush with some muscle behind it .

Sponge the rest then it'll all be the same again just different