Blending methods for adding and uniformly mixing a small fraction of relatively small particles (additives) to a bulk particulate powder of larger size than the additives. In particular, the present invention provides blending methods for adding and uniformly mixing a small percentage of flow/fluidization additives into fine powders, especially fine paint powders. The fine powder and additives are first pre-mixed for macro-scale homogeneity and then further mixed at a micro-scale (such as with a screen mixing process) for micro-scale homogeneity. With these methods, optimum dispersions and maximum functionalities of additives can be obtained and the disadvantages caused by severe agglomerates of additives can be avoided.