Then, you will need to add a thin coat of spackling compound to the spots that you have scraped away. This will eliminate the ridges between a scraped surface and the old paint that remains. When the spackling compound dries, sand the area using medium sand paper, and then give the area a brushing with fine grit paper to finish it off.
Repairing Cracks and Holes: Brush away loose paint and debris from holes and cracks with a dry rag. Wet the rag slightly and moisten the edges around the hole or crack, and then fill with spackling compound using a spackle blade to smooth it out. You may need to apply more than one coat, once the spackling compound dries. When the final coat is dry, sand it with a piece of fine sandpaper.
Preparing a Glossy Surface: Oil-based paint (also called oil-based enamel, or alkyd paint) surfaces are very non-porous and it is difficult to adhere paint, or even primer, to them.
One option is to use a sanding block (a piece of sandpaper wrapped around or glued on a block of wood) and work in a circular motion along the wall, trim, and woodwork. After you have sanded, wipe down the walls with a damp cloth and allow them to dry thoroughly.