I do use Whey in a post workout shake, but it didn't do me any good until I started adding other things, like oatmeal, flax seed, Chia seed, peanut butter, Coconut oil, milk, and the followed it an hr or so later by a protein/carb meal.
I do consume about 75g of protein through the day though shakes between Whey, hemp, and casein, but they are part of a larger diet, that will assist me in gaining mass.
Protein powder does not equal real food. It's a supplement.
But to answer your question, best would be post workout or in waking. When you're not working out.