I have some framing around an attic door in my house that consists of just some 2x4's screwed (and maybe glued?) to the ceiling. They look pretty rough with some knot holes, rough edges, etc. I might be able to take them down, plane them, sand them, etc. but it would be easier to just coat it with something that I can sand in-place and repaint. The nail or screw holes are filled in and I can't tell how it's attached, so getting it down will be pretty obnoxious.
Will normal wood filler work if the wood is already painted? If not, what else could I use?