Painting - Painting pre-cast concrete mantel/hearth

I have a pre-cast concrete mantel and hearth that I would like to eventually paint with some sort of faux finish. But first I want to make the surface smooth. It has 1/2" mortar joints between sections and small holes that rock salt creates. What do I use to fill these to smooth the surface of the concrete? What would I prime it with prior to painting the faux finish?

Thanks, Debby

Faux finishing a concrete mantel would be a first for me. Are the holes that obvious? I would use Durabond regular and skim coat these areas. A lightweight pre-mix like Dap should work ok. Lightly sanding first may help the skim coat process. The 1/2 inch joints use sanded grout. I use Sherwin Williams Pro Block latex. Or equivalent. Two finish coats of base coat. The SW "Illusions" latex glaze is a wonderful product. I start with 1 part paint and 3 part glaze. Natural sea sponge, smooth rag, stiff bristle brush, etc. A chamois has a great look. Possibilities are endless. :)

I don't know that durabond would hold to the concrete. Read the label. If it does, then go ahead and use it. Otherwise, I'd use a cementous material. Quickrete makes a concrete resurfacer that would get the mantel smooth.