The main difference is in the 1st level training, (OFT Level 1) which focuses on relaxing the nervous system. The OFT touch is applied to the spine, kidneys and adrenals to allow the Chi Nei Tsang to go far deeper when the abdomen is finally touched. The OFT touch on the back is directly impacting the water element.
This approach is based on Andrews many years of experience with Chi Nei Tsang where he noticed that it took a long time with Chi Nei Tsang for people to feel safe enough to feel without the minds involvement. Andrew developed OFT so that the Taoist Inner Alchemy healing principles behind Chi Nei Tsang could be experienced first hand, rather then being taught intellectually.
The other main difference is that when you are learning the Chi Nei Tsang on the abdomen in level 2 and level 3, Andrew is sharing what he has found to be most effective over many years of his own practice. There is less emphasis on learning many techniques and manipulations and more on developing sensitivity and embodiment of the healing principles that are at the root of lasting change.