There are no other methods. Cast is applied for immobilization. It is the basic treatment available. If possible ask doctor for fibercast instead of POP, it will be lighter .Keep it for 3-4weeks or as advised by your doctor.
Hello. Based on the history you have given I think you should know that harline fracture appear as a very faint line in the x-ray and the fractured bone generally remains aligned in the normal position without any displacement. The main logic behind applying plaster of Paris is to maintain that alignment and avoid bone displacement. The displacement might end up causing improper union of the fractured ends leading to abnormal movements and abnormal appearance of the fractured part. Sometimes displacement can also affect the nearby nerves and blood vessels supplying that area. Pop is the basic and simple method use to support bone healing in a proper way, all other techniques are rarely followed in simple situation like yours. If you are still not satisfied kindly consult a orthopedic surgeon for further queries.