Citadel Corax White Base paint is designed to give a smooth, solid white color over an undercoat and for that reason this will almost always be the first paint you use on a miniature. Shake the white paint before using (you can make this easier by adding an agitator ball).
The white paint can be a bit thick sometimes and then you just add a few drops of water on your pallet. You really don't need a lot of water. Something to watch out for is to make sure you don't apply too much paint so that you don't start hiding details.
Another important functionality of this white paint is that it not only covers the undercoat, but also covers other colors. So if you later miss something about this color, you can easily paint over it with this Corax White base paint.
The color of Citadel Corax White (21-52) is similar to: Old Citadel Smelly Primer; Vallejo Game Color White Primer (72002); Vallejo Model Color Foundation White (70919); Instar Arctic White; Reaper Master Brush-on Primer (9108); Privateer Press P3 Morrow white; Coat D'arms Gray Primer (141).