Are there any plasters that I can apply to a concrete countertop which will then be sealed with a 2 part epoxy sealant?

Stacy,
I just can across your post. Sorry for the delayed answer. I would stick with a product such as Skimstone, which can be applied in a similar look to some of the plasters, but it is a portland cement based product, and the epoxy coatings will bond better. I would think the surface would also be more durable, since the Skimstone is designed for floors, and the associated traffic they will experience. Regardless, you will definitely want to do a sample before attempting anything.
Rick