The pool is drained, which has to be done with care — an empty pool in wet ground can shift or float, and the water table in parts of New Jersey is high enough for that to be a real risk rather than a theoretical one. The solution is applied section by section, worked over the surface and rinsed before it can etch too deeply. Everything is then neutralised and the waste handled properly, not simply flushed into the yard.
This is not a job for a homeowner with a bottle of acid. The chemicals are hazardous, the timing matters, and an over-etched surface cannot be un-etched.