On the ceiling, you can most often find a finish using paint, less often whitewashing. First, exfoliating fragments are removed when using a metal spatula. All cracks are expanded to hard walls and base, then to cover and eliminate these defects. With whitewashing you will have to tinker longer, here you must first moisten the surface of the ceiling with a wet roller, after the ceiling is saturated, the same metal spatula is taken and the same work is done to remove the old layer. Old wallpapers are also moistened in order not to leave excess on the wall. It is not always advisable to remove the old paint from the windows or doors, this is usually done only if there are obvious traces of old age on the surface: cracks, chips. All surfaces that were previously covered with oil paint, before applying a new layer, it is advisable to treat with sandpaper, which will create the best adhesion to new layers of paint.
In order to remove the paint from these objects, you can apply two main methods: chemical, using reagents, or mechanical, using tools. Chemical reagents are various solvents or alkalis with the addition of a thickener, which will not allow the composition to dry very quickly and will not create subtexts on the surface.