Interesting topic.

I think alot of people wrongly believe that the TrA training is about "activating the core" during everyday painful tasks. This is not true.

The most effective method is, yes, using sensory methods to get semi-isolated activation of the TrA. This is neccesary to know wether or not it's firing properly without ultrasound imaging.

After a bout of activation (voluntary contraction), there is increased activation of the TrA in other exercises. Just doing the TrA activation will not do anything at all.

However, as some people have suggested, without a proper examination of the core muscles every method is guesswork. Tight abdominal muscles and hip muscles should be spotted during examination.