We lived in a house built ca 1833 which had a wooden wall covered with milk paint. It can be removed with trisodium phosphate, found in a hardware store. Just ask for TSP. Mix some with warm water in a spray bottle, then spray it onto the paint, then put a sheet of paper towel on it, spray the paper towel, pat it down to cling to the surface, and wait. In a few minutes something will seep onto the paper towel, softening the paint. Then the paint can be wiped away. It's not smelly, but does use a lot of paper towels.