It would be contraindicated to apply manual techniques immed over a fracture. However, for a simple displaced fracture mt's could be used to other areas of affected lung.

If segement is flail, you need to be well away from the whole flail area.

Remember, lung beneath fracture(s) will often be contused, and will usually resolve spontaneously.

Positioning to preferentially ventilate affected lung is crucial.
If the patient is well enough, sit out of bed/ mobilise. This will be as effective, if not more efective than manual techniques alone. It also has the benefit of being functional, and psychologically the patient will be more agreeable to the patient, whilst improving lung ventilation generally and specifically.

Good analgesia is critical to any treatment.