I was a PT for almost four decades. Learned all kinds of "mobilization" techniques in my early years as "manipulation" was pretty much taboo for us. I met a maverick chiro who was willing to help me learn some basic manipulation stuff and during that time things started to open up a bit for PTs in some states as far as manipulation. I had better luck with the stuff he taught me than the Myofascial and mobilization and positioning techniques that I had learned before. However, I was real careful to not use manipulation on people who had severe disk disease or any kind of severe vertebral instability.
Manipulation worked best in the thoracic region where the facet joints are more fixed due to the costocondral joints on the anterior aspect. It seemed like a precise manipulation of the appropriate level in the thoracic region could completely relieve an individual who was in pretty severe pain. In the lumbar and cervical regions the movements to manipulate were much more limited by the patient's muscle guarding and therefore weren't as effective.
Just my two cents as a PT.