I learned this tip from Food Scientist Alton Brown from the food channel. Garllic powder needs to be reconstituted with water before adding to any food. Make a paste out of it first with water then add to your potatoes (or anything). Food tends to encapsulate dry garlic powder making you use much more than is needed.
Warning: The garlic powder paste is much more powerful than when adding directly to dishes...use a light hand and taste.