Rib pain is common with lung infection, especially if the plueral space becomes "sticky". Breathing exercises to both inflate the lung and the rib cage would be good. Think laterally. Get the client to go and buy a packet of ballons. Ask them to blow up 10 balloons twice a day for a week and you might get a great result.
I would not want ot use any device such as ultrasound over a previously infected tissue. Use gentle rib mobs in prone and also in sidelying. Let us know how you get on.