I did not have any exposed fiberglass insulation when I painted my ceiling. However, I think exposed fiberglass, especially the pink side, would not be good. I'd expect it to act like a sponge. If you have the paper side facing into the room, you are probably okay. Another option would be to install blocks of rigid foam (think pink or blue) and seal it in place with expanding spray foam from a can. Depending on how deep the cavity is, you may need more that 1 layer. Or, put the fiber glass in, and cap it with the rigid foam. But don't compress the fiberglass too much. You need the air space for it to work properly.
Chris
LVHR
