hands-on soft tissue work is not in the scope of practice of certified personal trainers. If you have the qualifications for it, then this will be regulated through the appropriate agency.
There are several techniques for self-manipulation which can fall into the scope of a personal trainer, such as MELT (Myofascial Energetic Length Technique) or the myofascial release techniques recommended through the corrective exercise continuum of the NASM CES certification. Those are done by the clients themselves based on evaluation and advice of a trainer.
Hope this helps.