What are people currently finding to be the most effective sourcing method for response rates? Linkedin, letters, email...or a combination?

I’m thinking of doing a video about building a world class advisory board (with no money) and raising money from banks and investors (using the boards contacts and credibility). Anyone interested in me doing this? If so I’ll record something this week and will use a case study where I have done this. Post yes in the comments and I’ll do it if enough interest.