I've used hydraulic cement years back. It works well. If I remember, it expands as it cures to seal the job. And you need to work reasonably fast. The stuff from years back was darker than the light grey wall. What I did was use the hydraulic cement, and then a product that was a thin coating meant to seal over the top- and did the whole wall in question. In other areas of that old house, I found that sloping the area right next to the house so the water would run away did the trick. If you have an area that may have some flexing that you want to seal, I think I would try a masons type caulk myself. Good luck.