Use gloves. Careful not to breath fumes. Try not to fill bucket more than half (water will bubble up when Muriatic is added to bucket). Replace water with each batch for consistent effect (acid will be variablt diluted as H+ used up). I have always poured directly down drain while running water without ill effect, but sodium bicarbonate would make sense. Not sure how long to soak rock or what to expect: I use muriatic all the time, but only to clean (tanks, skimmer, PH, etc)