The foot, like the knee can be used effectively for manipulating the thoracic spine. You can do this by having the client in sitting or long-sitting, ask them to place their hands behing their neck for support, and using the breath ask them to arch over your feet as you sit behing them placing pressure on the appropriate thoacic region/s.

That siad perhaps the best massage and manipulation of the body with the foot is the Chavutti-Thai Massage. I have experienced this and it is definately to be recommended.

CHAVUTTI-THAI MASSAGE (pronounced: cha-vo-te-tie)

Chavutti-Thai Massage was developed and founded by Kingsley Ogedengbe.

He combined the elements and benefits of two styles of massage, Traditional Thai Massage created 2,500 yrs ago in the Buddhist Temple of Thailand and Chavutti-Thirumal used to prepare the Kalari Martial Artists and Kathakali dancers of India.

Chavutti-ThaiTM massage is a full body oil massage, which begin with Traditional Thai twists and stretches design to open and relax your body.
The practitioner then holds onto a rope suspended above their head and applies warm therapeutic oil with their bare feet using long deep rhythmical strokes (chavutti).
The foot is actually more sensitive than the hand and is able to cover the full length of the body with each sweeping strokes from head to toes.

During a Chavutti-ThaiTM massage the chakra and meridian lines in the body are massaged releasing blocked energy making you feel light, refreshed and energized.