A. Steve Thomas, a construction estimator in Columbus, Ohio, with many years’ experience in the stucco trade, responds: I would advise against either hydraulic cement or any "hurry-up" product for the base coats. The reason is simple: You can almost bet the surface you’re attempting to patch (and match) was not created using these products, but a less expensive, standard cement/lime/sand mixture.
The capillary suction of the undercoats — their tendency to absorb moisture from the finish coat — will directly affect the drying time and therefore the color of the top coat. The hard, fast-drying products you refer to are much less absorptive than a standard cement mix. Even if you use the exact same finish-coat recipe as the original, it...
to read the full article.