When using ink in an airbrush, only use water-based inks made for the airbrush. These are known as acrylic inks or paints.
The most common reason for airbrush clogs and blockages comes from using a dirty airbrush. Clean the nozzle and all parts before and after each use. To prevent chlorine or minerals from damaging small airbrush parts, use distilled water to mix inks and clean equipment.
When ink does not flow smoothly from an airbrush nozzle, you can try a larger nozzle, raising the air pressure or diluting the ink with water or the flow medium recommended for the ink brand you are using. If using a flow medium mix it with the ink in the quantities recommended on the flow medium bottle.
Before using the ink on your final project, test the spray paper, cardboard or other material to make sure you get an even paint flow. Make adjustments to your air pressure and nozzle to determine the best flow. When applying it to the object you want to airbrush, make sure the object or skin is clean. You can clean the item with alcohol or an alcohol dipped swab before starting. Ensure that the stencil you use is taped to the area and all the design edges lay flat. Start airbrushing from the outside corners to the interior side and always allow one ink to dry before applying another.