When planting up pots,planters and hanging baskets,i always use water retaining granuals mixed into compost-- dont just sprinkle-- mix ,because sprinkled, it can form a mass of jelly, no good to plant or soil. Something else to try, moss mixed in to compost, really holds the moisture, also blotting paper at the bottom of basket etc, talking of bottoms,try disposable nappies, these really soak up fluid. one last thing ! water little and often, to much water on dry compost is useless and wastes water and time,and if you can make it luke warm water just to start WOW