Honestly, none of these techniques work to build actual “trust”.
They will (at best) make people perceive you as more likeable, which is not nearly the same thing.
Trust is built over time and through honesty. I’d rather trust someone who honestly tells me he is not interested in my bullshit story than some who pretends to care and asks bullshit questions.
Anyone with a bit of knowledge of human nature can spot fake interest from a mile away.
A lot of the mentioned “techniques” also sound too cliché or are ambigious in my opinion. Yeah, someone mimicking my body posture may indicate trust —but it may also indicate a million other things.
Given that the opinions and techniques come from an “FBI expert” I am actually not surprised. They sometimes mistake assumptions for knowledge and occasional coincidence for a proven system. But people suck it up, because it’s from an “FBI expert”.