Start with a coat of primer/sealer. If you’re painting the cabinets a color other than white, ask the paint store to tint the primer to match your top coat.
That way, you might be able to get by with just one finish coat. Otherwise you’ll most likely need two coats of paint over the white primer.
You can choose to paint only the faces of the cabinet boxes, as shown, or the interior as well. Use a brush if you paint the interiors.