A "dull looking" surface is dull because it is rough on a microscopic scale. The fine-scale roughness causes diffuse reflection, thus the dull appearance. The fine-scale roughness may not be apparent with a mechanical profilometer or visual examination, but will be apparent using optical interference surface measuring techniques or in the scanning electron microscope at high tilt angles.
This fine scale roughness will increase the surface area available for adsorption of contaminants, and provide greater potential for retention of microbes. You may be defeating your purpose.
You can generate a dull surface in stainless steel by etching in nitric acid with additions of etching salts, which are flourides.