While paint can conceal a lot of damage, it can't cover everything. It can't fill in dents or holes, which must be repaired before you start for best results. If you're trying to paint something made of metal which has developed pitting, though, you may be wondering how you can do this, since many substances don't adhere well to metal. Auto body fillers work very well for preparing metal items for painting.
Sand the item with a coarse sandpaper, 80 to 150 grit. If it already has a coat of paint, sand until you see bare metal. Wipe off the dust with a tack cloth or vacuum out the dust.
Clean off rust, if there is any present. Sanding or brushing works well for a sturdy object, like a door, and you can also apply a rust removal product like naval jelly. If your item is more delicate, consider something a little gentler, like soaking the item in vinegar or applying a paste of baking soda and water. Wash off any chemicals that you use before proceeding.
Clean the item with a mild household cleaner, if needed. Dry your item immediately.
Mix the chemicals in your auto body filler kit according to the instructions. Apply some of the filler to the pitted area, then spread with a plastic putty knife. It's better to have too much filler than too little. Wait for the filler to dry.
Sand the filler until the repair is flush with the rest of the item. If your item is small, sand by hand; for a large repair, use a vibrating orbital sander or a palm sander. Start with a coarse sandpaper, about 100 grit, and move up to a finer one, up to 400 grit.