Prepping the Exposed Area

• 1). Scrape the rust particles and scales with a putty knife or flathead screwdriver. Ensure you get both sides of the area in case the rust has seeped through.
  
  
• 2). Cut out any rotted through metal with a pair of tin snips or a file making sure to remove any metal that has rusted through. This will leave a hole in the metal.
  
  
• 3). Sand the rusted surface with a 220-grit sandpaper. A red Scotch-Brite pad will also work. Sand until you are down to solid, shiny metal.
  
  
• 4). Sand out the area with a lighter sandpaper to feather out into the remaining paint on the surface. Sand until you can see the spread of layers of paint, primer and clear coat.
  
  
• 5). Clean the area with a plastic brush and soap. Dawn dishwashing soap works well. Ensure you rinse the soap and let the area dry. You can use a hair dryer to help speed the drying process.
  
  
• 6). Tape off the exposed area. This is to prevent spreading the primer to a painted surface.
  
  
• 7). Wipe the exposed area with alcohol before priming. Rubbing alcohol dabbed on a clean cloth works best to remove the oils left by the soap.
  
  
• 8). Paint the primer to the surface. You will need to do this immediately because the rust process starts as soon as the bare metal is exposed. Spray the primer evenly over the exposed area. The primer will need 24 hours to dry.
  
  

Adding the Bondo

• 1). Sand the primered surface with 220-grit sandpaper. You can also use a red Scotch-Brite pad. This will rough up the surface so that the Bondo will have something to stick to. Do not scrub off the primer; you just want to rough it up.
  
  
• 2). Mix the hardener and the filler of the Bondo. Mix it on a piece of sheet metal or cardboard. The instructions for mixing will be on the Bondo package. The general rule of thumb is that using more hardener will make it dry faster. The mix will form to a solid color when it is mixed properly and thoroughly.
  
  
• 3). Scrape the Bondo on to the sanded surface with a plastic squeegee. Even out the area with a metal putty knife. Scrape off any excess.
  
  
• 4). Allow the surface to sit in heat for 15 to 20 minutes. This will allow the Bondo to cure. The touch test will consist of touching the Bondo; if it feels tacky, then it is still drying. Allow it to harden before sanding it out.
  
  
• 5). Sand out the area lightly with your sandpaper to ensure you used the right amount of Bondo. In the instance that any area has a darker color than the other areas, you will need to re-apply the Bondo until the whole area is level. This will take trial and error to ensure you get the area right.
  
  
• 6). Sand out the area again to ensure all the low spots are filled and the surface is flat. Inspect for any dips or low spots.
  
  
• 7). Spray guide coat on the area to expose the low spots. This will help to ensure accuracy. The guide coat can be purchased at an auto parts store. The guide coat is made exclusively for bringing out any flaws in the filling process. This will darken the dipped areas. You will need to re-apply Bondo to bring the low spots flush with the rest. Sand all the raised surfaces down.
  
  
• 8). Repeat this process until the whole area is smooth and flush. The area is ready for primer.
  
  

Priming and Painting

• 1). Spray the primer coating to the affected area. This will also help fill in any imperfect areas.
  
  
• 2). Wet sand the area with a 500- to 600-grit sandpaper. Sand until the whole surface is smooth. Dry it off with a clean towel.
  
  
• 3). Spray the lacquer primer onto the surface. Allow the primer to dry for 24 hours.
  
  
• 4). Paint the surface with your desired paint color. You can match the paint at your local paint store. You can also buy the paint in a spray can at the local parts store. The parts store will tell you where to find the paint code for your vehicle.
  
  
• 5). Remove the masking tape from your vehicle. You can lightly wet sand the whole area with a 500- to 600-grit sand paper to ensure the whole area is smooth. This is optional.