I have used pressure biofeedback only occassionaly in my practice. I am fortunate to have access to a Real Time Ultrasound Unit at my practice and find that this gives a much more accurate idea of isolating the TA. It can also be used in functional positions - eg lifting, bending, marching on the spot. Many patients have been referred for real time ultrasound imaging to check they are using their core stabilisers correctly after some exposure to the pressure biofeedback and it is not uncommon for them to have inappropriate activation of the muscles (eg cocontraction or phasic contractions). So I would thouroughly reccommend ultrasound training if possible.