Remove the cabinet doors. I’ve found an easy way to assure the doors go back in the right places once you’ve removed them: number each door in an inconspicuous place on the wood (where the hinge will be) and place a piece of tape over the number (so that you don’t accidentally paint over it!) Write the same number on the inside of the cabinet frame (just inside the cabinet) placing a piece of tape over it as well.
Sand the cabinet doors and drawer fronts. Take the cabinet doors outside in an open area to sand, because this will produce a lot of dust. Wear a dust mask. Place some plywood on some sawhorses then lay the cabinet door on top for a workable surface. Use a palm sander with 50 grit sandpaper to bring the cabinet door to the bare wood and ensure proper adhesive of the oil base primer.
Sand the cabinet frames. Since you have the added challenge of sanding inside, you’ll want to avoid producing lots of dust. Instead of traditional sandpaper, use a chemical solution called liquid sandpaper. It will slightly melt the varnish and clean the surface so that the oil base primer can be applied.
Apply two coats of oil-based primer to the doors and drawer fronts. Spraying a lacquer oil-based primer is more efficient as the drying time is typically 15 minutes between primer coats – lots less time waiting as compared with waiting on other typical oil-based primers. Sand between coats. Since lacquer primer does not raise the wood grain, sanding will be easier. Allow at least 24 hours before applying finish coats of paint. Then spray or brush two oil-based finish coats waiting 24 hours between coats. Spraying creates a much smoother finish.
Apply two coats oil-based primer to the cabinet frames. Brush the paint. Let the primer dry.
Then the preparation at this point will consider caulking obvious cracks in the trim and where the wall meets the cabinet frame, glazing compound works well for nail holes, alike version of painters putty, also a spackling compound needs to be applied on certain joints on the cabinet frame to slightly hiding where the cabinets are piece together Sand between coats. Apply two oil-based finish coats. Waiting 24 hours between coats.
Finally, a word of advice. Painting requires a great amount of skill, patience, and attention to detail that can only be learned through experience. The kitchen is an important focus point of the home interior. You want a factory finish, not just a coat of paint. Painting kitchen cabinets is a craft. Hiring a real craftsman to handle the project is a much less expensive option compared with purchasing and installing a new set of kitchen cabinets.