When I suggest professionals write as part of their brand building the very thought brings a sense of fear that they have nothing to say.
Yet these same people can stand in front of a whiteboard and talk for hours on their area of expertise. Chat over coffee and hold a conversation with a prospect. Offer an opinion when required.
Do not assume what you have to say is either common knowledge or unwanted.
I am pretty sure there is a lot of good rattling around in your head and like song writers, you have to be prolific and occasionally you will strike gold.
Take the first step.