Methods of manufacturing drug-coated medical devices having a porous coatings thereon. The pores are created by solid particle additives added to a mixture comprising a solvent, a drug, and a polymer to create a suspension, which is applied to the medical device. The method includes adding a surfactant to the mixture to prevent or decrease flocculation of the solid particle additives. Another method is provided that includes spraying a suspension on a medical device that comprises solid particle additives, a drug, and a polymer and analyzing the distribution of the solid particle additives in the suspension.