Citadel The Fang Base paint is designed to give a smooth, solid blue-grey color over an undercoat and for that reason this will almost always be the first paint you use on a miniature. Shake the blue-grey paint before using (you can make this easier by adding an agitator ball).
The blue-grey paint can be a bit thick sometimes and then you just add a few drops of water to 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 blue-gray 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 The Fang base paint.
The color of Citadel The Fang (21-32) is similar to: The Army Painter Wolf Gray (WP1119); Old Citadel Shadow Grey; Vallejo Game Color Sombre Gray (72048); Vallejo Model Color Oxford Blue (70807); Instar Gray Blue; Reaper Master Twilight Blue (9020); Coat D'arms Shadow Gray (150).