Long copy
Long copy is explanatory text that does its job whether or not it is read, because its visible existence signals there is something to substantiate.
How it works
A claim stated bare reads as too good to believe. The same claim with three hundred words beneath it reads as a position someone is prepared to defend, even to the reader who never gets past the headline. The length is also free wherever the audience has nothing else to do: a poster glanced at for three seconds becomes one read for a minute at no extra cost. The people who actually read it are the undecided, which is the one group where reading changes something.
What it changes for a personal brand
Stop cutting your explanation down to what you think people will read. Write the full version, put it where the undecided will find it, and let its visible existence do the work for everyone who never gets past the first line.