Strip the frame. Using bicycle-specific tools, remove the headset, drivetrain, handlebars, seat, stem, seat post, wheels and any other components from your fixie. If you don't have the tools to dismantle your bicycle yourself, your local shop can do it for a small fee. During refinishing, keep your work area well ventilated to prevent inhalation of any toxins.
Sand and refinish the frame to prepare it for paint. If your frame exhibits any corrosion, paint chips or grime, you'll want to clean, sand and polish the frame until the texture is uniform and smooth. No. 320 grit sandpaper can be used to scrub off old paint, with enough elbow grease.
Use a phosphoric-acid-based rust remover to remove corrosion. The phosphoric acid will eat away at the rust, allowing you to sand it off and restore the frame's original smooth texture. In a pinch, aluminum foil and water or a bit of cola can also work as a rust remover, but may leave residue on the frame.
Clean the frame using a solvent. A solvent cleaner will remove any hand oils and other contaminants that can prevent the primer from adhering to the frame. Use latex gloves to handle the frame while cleaning it, and afterward to prevent recontamination.
Seal off any openings using newspaper and masking tape. The bottom bracket shell, head tube, seat tube and rack and water bottle bosses should be sealed so paint doesn't get inside the frame.
Painting and Refinishing
Hang the bicycle frame in a well-ventilated area. You'll want to use a shed or garage where getting paint on the floor or walls won't matter. Make sure the area offers good airflow, as many of the toxins in paints, primers and solvents are harmful if inhaled. Use a mask is necessary.
Apply a layer of zinc-based primer. A zinc primer will work like an electric battery, absorbing the corrosion that would otherwise affect the metal of the frame. Sooner or later, moisture will work its way under your paint, but a zinc-based primer will prevent that moisture from causing corrosion to the frame.
Apply a base coat to the frame in the desired color using a paint sprayer or brush, after the primer is completely dry. A paint sprayer or spray can will give a more even coat, but a brush can be used deliberately for texture.
Mask off any patterns and re-coat the frame in a second color after the base coat is completely dry. This is optional, but now is the opportunity to let your creativity show by masking off the base coat and applying a second or third coat in different colors for a unique look.
Finish the frame with a clear coat. An enamel clear coat will protect your paint job from scuffs and give it a high gloss. Your frame is ready for reassembly. You may have to sand out the drop-outs, bottom bracket shell or headset if paint made its way into the frame during the painting process.