How do you remove bad stains from a gunite pool that has lost some of its smooth finish?

this works only on marcite pools, lower pH first to 7.0 then lower chlorine to 0 ppm , shut off pump, springle citric acid about 4 lbs, let it settle to the bottom, let it sit 24 hrs with no movement, then turn on pump, shock with 1 gal chlorine and let it run 12 hrs then shock again 1 gal and brush away citric acid. Also bring your pH up slowly. This should elminate staining then be sure to use a metal out for future use.