You first need to make sure that the surface is clean of any soot that may be there. You can wash with an ammonia and water solution and allow the stone to dry for a day or so before starting to paint.

You will want to prime the stone with an acrylic primer such as Ben Moore Fresh Start Acrylic Primer. The finish paint can be the same as you used on your walls and I would think that you will need to apply two coats of finish over the primer.

Hope this helps out.

Thank you for replying. I'm going to give it a try.