Clean them first with a good degreaser then 120-180 grit paper, sanded with the grain should be fine. You won't be able to sand between coats very well with a latex paint so you may be better off to get a good, smooth, clean surface before you start. Then one coat of kilz II and 2 coats of paint should do fine.
I use wax on the backs of the doors where they close against the cabinets to keep them from sticking and ruining the paint. Make sure the paint is dry before you rub the wax on. It will feel dry to the touch within 6 hours and you can apply it then but it will take days for the paint to cure to a durable finish.
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