Some tips for cultured marble sink repair include avoiding abrasive or harsh cleaners or chemicals such as ammonia, bleach, and acetone. One should also avoid using very hot water. Another tip is to use sandpaper to sand out small, shallow pits.
If one uses sandpaper, it should be 800 to 1200 grit and can be used wet or dry. Before doing this, the sink drain needs to be covered up with masking tape to prevent scratching it.
If the pits are deep, they can be filled in with two part epoxy. The pit first needs to be scraped out with a razor blade knife, and the area needs to be dry and clean. One should mix the epoxy on a flat surface such as a trowel, then apply it to the pit and smooth it out. It should be left to set, then sanded with 400 to 600 grit.
Unfortunately, since cultured marble is polished, both sanding and filling in pits might be somewhat visible, since the polish is necessarily rubbed off. One way to remedy this is to dye the repaired area the same color as the sink. Another remedy is to buy a repair kit for fiberglass boat exteriors, or to brush a clear gel over the repaired area after it has dried completely.