BROKEN COLOUR techniques are great for less than perfect walls!
Broken Colour Techniques are generally applied onto large surfaces and are ideal for walls. They involve the manipulation of glaze. This is a translucent veil of colour that is applied over an opaque base coat, and is then removed or distressed by various means so as to expose the base coat in places. Effects such as colourwashing and ragging fall into this category.
Many paint effects have their roots in earlier centuries and seem to come in and out of fashion fairly rapidly. They do provide quick cover ups for less than perfect plastering or can distract the eye from textured surfaces that would be costly to remove.