Disassemble the cabinet with a screwdriver, taking off all the hinges and hardware.
Set up the vibrating sander with rough sandpaper. Run it over each surface of the wood, taking off the white-washed layer on the top.
Vacuum up the dust.
Put a medium sandpaper sheet in your sander. Run it over each of the surfaces again, taking off the top layer of the wood and exposing the bare grain underneath. Vacuum.
Sand the cabinet a third time, with fine sandpaper, to smooth out the surface. Sand with the grain of the wood. Vacuum thoroughly.
Brush on wood conditioner with a paintbrush, covering each section of the cabinet and brushing with the grain. The conditioner should soak into the wood as you apply it. Let it set for 24 hours. The cabinet is now ready for staining.