Spray in a steady back-and-forth motion, slightly overlapping each stroke. Apply 2 or more light coats a few minutes apart, then allow 15 minutes to dry. Next, shake the can of Stops Rust Hammered spray paint for 1 minute after the mixing ball begins to rattle. Hold the paint can 12-14” from the toolbox and apply 1-2 light coats. Spray Paint Over Rust. After your surface is clean, dull, dry and primed appropriately, spray Krylon Rust Protector or Rust Tough Enamel on your well-prepared surface. Apply multiple thin coats to prevent runs and drips. Dries to the touch in 8 minutes and tack free in 15 minutes. Still have questions on how to spray paint over rust? Ask Krylon. how to paint over rust. The first step in dealing with exterior rust is to clean it as thoroughly as possible. In most cases, painting directly over rust without scraping it off is similar to filling a tooth without first drilling the cavity–the surface underneath will continue to corrode underneath the fine exterior. Use a wire brush to scrape away any loose rust or flaking paint, and use sandpaper to remove particulates and smooth out the surface. You can paint over it once you are done, or you can just use it as a standalone coat of paint. If you want to paint rusty metal, and you don’t care if it looks really good or not, rust converting primer is a great option, and it is a lot faster and cheaper than sending all the rust off of the metal before you paint it. Use a brush or paint roller to apply the exterior paint, if you want to ensure you reach every crevice of the steel. Hold a brush at the base of the handle to ensure you have good control of your brush strokes. Use spray paint, if you want to ensure there is an even coat. .