I try to avoid acid as much as I can. I see a lot of floors that were poorly etched and the floor was not properly cleaned. (you have to put a strong base on the floor several times. aka baking soda, to make sure there is no more acid in the floor.) If you dont get all of the acid out it will...
Ive been a floor prep specialist since 1978 here, and when you run into fiber concrete its very hard to grind for prep. If your using a Dimabrush it means your not likely to be using a proper grinder for the job at hand. Not to offend anyone but a Diamabrush is more like a high end sanding...