I had a leak around my chimney flashing, and the plaster in one room got water damaged: it's plaster over brick, and the plaster is now crumbly and powdery in spots. The rest of the plaster is sound, and the leak has been fixed. How can I repair this? I will not consider drywall, I'd rather recoat with plaster if possible. Can someone tell me how to go about it...I'm pretty sure I have to scrape off the crumbly bits, but what is the next step, and do I have to go down to the bare brick?