It's an effective way to differentiate yourself by zoning in on how you can add value to a company. Your message and image should be consistent — if you're interviewing with multiple people at one company, a flip flopping brand would give the impression that you don't know what are your strengths. People always hate writing cover letters because they don't know where to start — a personal brand is the answer and it's what you want to convey in that first piece of communication with a prospective employer. Your personal brand is what sets you apart from others that may have similar resumes to your own. Start with these questions: What makes you stand out, and what do you stand for? Build your brand from there.
I wish I knew.