Sand your countertop and sink. This will dull the finish of the cultured marble and make it easier for the concrete to adhere.
Mix your Feather Finish concrete. Pour some of the dry mix into your drywall tray, add water and mix it with a small putty knife. You want to mix it to the consistency of thick pancake batter. After mixing it, let it sit for a few minutes and then mix it again. Now it is ready to work with.
Apply your first coat of concrete to the entire cultured marble countertop and any backsplash. You want to apply a THIN coat–do not strive for full coverage on the first coat.
Next, apply it to the sink basin. You have to do this with your fingers. You should protect your skin with gloves. Spread it around as best you can. Again, it will be messy and you will see finger marks.