We whitewashed the ceilings in our bedroom, bath and kitchen. The ceiings were unfinished tongue & groove pine, and we used a mixture of paint & water (I think it was 3 parts paint to 1 part water). The color was SW Shoji White. It was painted on then wiped off with a cloth. Our effect was more transparent than this photo shows, but it would be easy to alter the effect by using more/less water, or varying the time lapse between painting and wiping, or wiping more or less paint off or even wiping with a less even pressure to give an older time-worn effect. I've attached pics taken during construction of the bedroom and kitchen ceilings.

And, by the way, to 1935chief, our carpenter "created" beams with 1x8 lumber. These "beams" spanned the width of the kitchen ceiling and also the great room (family room at one end and dining at the other). He also "created" beam headers for the cased openings between the kitchen and family room and at the cased opening for the recessed wine bar in the dining room.