Light surface sratches in cultured marble tops can easily be removed by using a buffer and buffing compound.We use a heavier buffer at the shop however any automotive buffer would work just as well.Buff out the scratches then apply a nice wax to restore the luster.Deeper scratches can also be removed by first wet sanding the scratches using 400 grit wet sand paper(use plenty of water)and a sanding block(a piece of wood 2" by 2" works nicely)Then buff with compound and apply wax.As a side note you can also give your top that "satin"look by using a buffer and a scratch pad.Pay close attention to the edges so you don't go thru the gelcoat.