If solids, especially pigments, are not broken down into smaller particles and spread evenly throughout the liquid base, the result is a poor paint quality. This can affect everything from leveling and sagging to color and gloss quality as well as other attributes.  Although additives can help with wetting in the beginning of the dispersion process and stabilization at the end, nothing can take the place of the mechanical means of breaking apart larger collections of particles into their finer counterparts.   There are various ways to do this from a disperser with a dissolver disc to a bead or basket mill.  The choice of equipment is dependent on the ingredients in the paint formulations and the degree to which they are easy or difficult to disperse.