As the most common secondary GI engine, the deserves special attention. Its primary control is the Subdivs (subdivisions) parameter. This determines how many paths of light are traced through the scene. A higher number results in a smoother, more accurate lighting solution but increases render time. For test renders, a lower Subdivs value (e.g., 500-1000) is sufficient. For final renders, you might increase it (e.g., 1500-3000) to smooth out any remaining splotchiness.
V-Ray uses two engines: (bright, direct bounces) and Secondary (soft, indirect bounces). vray render settings for sketchup