The larger question pertains to the concrete slab within your garage. If you flush with water, but do not neutralize the acid on your concrete slab, you run the risk of having residual acid remain in the concrete pores which will continue to etch. This can cause your concrete to break down (become brittle). Water has a neutral pH so it does not neutralize the acid, it only dilutes it. This is a common occurrence with DIY applicators that only rinse their floors with water and question why years later the slab underneath their coating is breaking apart into pieces or becoming dusty.
To neutralize, you will want to spray the surface with a solution of either soda ash (one pound of sodium carbonate per five gallons of water) or ammonia (one cup of household ammonia per gallon of water). Amonia is easier to work with and will usually neutralize the concrete in one application. Spread the ammonia uniformly over the concrete in the manner that was done with the etching acid and keep the surface wet. Basically you are repeating the same process by which you etched the floor, except with ammonia.
