1928 brick house in Michgan. Interiors side of the exteriot walls are like stone, I guessing it's the old button board plaster. In the sloped ceiling, there are seams that look like their oozing joint compound out on the surface, but it's dry and has been for a long time. Can I just grind this off and paint over it? I also notice some very small cracks in the horizontal ceiling, probably a 1/16th of an inch or less that also is straight enough to be a seam. Is there a plaster joint compound that can be used on these?