Citadel White Scar Layer Paint is designed to be multi-layered. This white color is slightly transparent, so you can use it to build your color over several layers until you're happy with it. Now the paint does require a bit of practice to use, but the results are well worth it.
The layer paints are best used as a 2-step highlight, so two paints for each color but this is a guideline. For example, White Scar can be combined with Ulthuan Grey. You start with the darker of the two and apply it to the surfaces that you want to finish with this white color.
Because the paint is a bit transparent you will continue to see the base color a bit, but by using White Scar together with Ulthuan Gray you can use that transparency to apply the layers. If you apply the lightest color after the darkest color in maybe 1 or two layers, the last highlight of the lightest color will ensure that you have a great result.
The color of Citadel White Scar (22-57) is similar to: The Army Painter Matt White (WP1102); Old Citadel Skull White; Vallejo Game Color Dead White (72001); Vallejo Model Color White (70951); Instar Arctic White; Rackham Eternal White (1); Reaper Master Pure White (9039); Privateer Press P3 Morrow white; Coat D'arms White (101); Scale75 White Matt.