Well, you have managed to stump the experts twice on this one. Why would anybody want to paint the inside of a fireplace? What happens when you strip this? Darned if I know the answer to either one. JayJ might have some input but he is probably busy painting the screens on his TV set and computer.
For what it's worth, if you use Citristrip for the firebrick, the smell should probably be gone in a day or so but I would wait a week at least before you try a fire in the fireplace. Don't use any kind of wash with this. You might want top call out a chimney sweep before you light a fire also. Since the fireplace has not been used in a while, the flue might have bird's nests or other obstructions in it. And with the paint and the stripper, you want to be sure that it draws well before the first fire.
Too bad that somebody never heard of painted metal fireplace screens. They are pretty much antiques now but they went in front of the fireplace and usually had scenes painted on them.