Attach an empty paint cup to the airbrush. Depress the trigger until all the excess ink comes out of the gun. Remove the paint cup from the airbrush. Fill a clean paint cup with rubbing alcohol and reconnect the cup to the airbrush.
Cover the tip of the airbrush with your finger and press the trigger to back flush the airbrush. This breaks up dried paint and debris by using pressure to send it into the paint cup. Spray the alcohol through the airbrush until it comes out clear.
Unscrew the paint cup. Remove the shell of the gun (the back). Unscrew the needle lock nut and gently pull out the needle. Clean the needle with a soft cloth.
Unscrew all four pieces of the head of the airbrush to disassemble it. The head contains four pieces---the nozzle cover, the air cap, the air cap body and the tip. Dip a cotton swab in rubbing alcohol and wipe down the inside and outside of each of the four components, making sure that all four pieces appear free of paint or debris.
Look inside the nozzle for built-up paint, cracks and warping if the airbrush still does not work properly. Use a magnifying glass or jeweler's loupe for a close look.
Soak all components of the tip in hot soapy water (110 degrees to 190 degrees F) for two hours. Reassemble the airbrush and fill the paint cup with an airbrush cleaning solution. Attach the paint cup and spray all of the solution through the airbrush.