I'm in the process of having a multifuel stove installed. My existing fireplace has been widened and rendered with cement. However, the finish isn't brilliant and dusts. I want to paint this with emulsion. Presumably using PVA to seal the surface is out as the heat from the stove will be too much for it. Will the emulsion take OK? Should I thin the first coat slightly to get a better seal? Has anyone any experience of doing this?