Don't wash it ! spray or roll on kilz primer. kilz is made to cover up smoke and other stains on paintable surfaces. Then pick out a good paint, behr premium, valspar or Benjamin Moore...use an acrylic paint ( latex, clean-up with soap/water ). make sure you always have good ventilation when doing any type of painting, even if paints have almost no smell and are non-toxic...spend the $$$ on a good paint and paint less often .
Use "BIN" brand primer. Just painting over smoke damaged walls/ceilings wont do it. The toxic waste will just bleed through. If that doesn't work then burn the place down and rebuild.
Clean the smoke of of with some sugar water. I don't mean mix water with sugar either lol bit of elbow grease it should come of no probs then happily paint away
White eggshell paint is the best way of covering any kinds of stain on ceiling, it will cover damp and smoke stains plus fire damaged ceiling(try remove excess whenever possible by simply washing with damp cloth and sugar soap)using this type of paint please insure rooms are well ventilated wear gloves and safety glasses to avoid splashes to eyes.Hope this helps.