Good tips for porcelain repair start with cleaning and drying the area well, followed by sanding the damaged section. Good repair kits are found in the paint section of home improvement stores according to realtor.com.
Choosing a filler kit that matches the color of the current porcelain is important for a quality repair. Realtor.com recommends applying a thin layer of filler once per day for one week, and allowing for adequate drying time. Circular motions for sanding the layers of filler is preferred. Keep in mind that using as little glaze as possible will make the repair seamless. Be sure to only sand the filler and the glaze over the repair to avoid scratching the rest of the porcelain.