The upper thoracic spine can be difficult to self mobilize. Normally a great way to modulate pain and relieve stiffness is cervical retraction with extension.
However, since this movement is not normally performed, it can be uncomfortable due to upper thoracic extension stiffness. Try this mobilization if your patient cannot tolerate (or is afraid to try) cervical retraction with extension in either supine or sitting.
Upper Thoracic Self Mobilization with Foam Roller