Anything you broadcast must be valuable on its own and fit the relationship; then watch who engages and turn that into one-to-one outreach.
The idea
Twice a year my inbox fills with reminders to change my clocks. My devices do that for me. Nobody sending those thought "Zvi needs this." I'm one of many on a list. Broadcasting can build mindshare with a big group, but only if what you send would be worth something on its own, and only if it fits the kind of relationship you have.
How to do it
Decide who should get it. The more important the relationship, the more likely something impersonal backfires.
Make it valuable in isolation. Some people may appreciate a discount on your services, but the test is whether they'd value what you send on its own.
Make it relevant to the relationship, a teaser of how useful you'd be up close. A real estate agent shares up-and-coming restaurants in a neighborhood. A lawyer explains a ruling that affects his clients. A consultant shares trends she's spotted in her clients' market.
Give people a window into your life, so they feel closer when you do reach out personally.
Harvest the signal. Notice who opens, clicks, replies or keeps liking your posts (often surprising people). They're the ones likely to pick up the phone. Reach them one-to-one.
Where you can, add a personal line per recipient. That's one-to-one relationships at scale.
Example
For a short while I emailed my whole database updates and resources I'd found useful. Most responses were good. But a few people I really cared about told me off for something that impersonal. I quit doing it and doubled down on personal outreach for those relationships. These days the broadcast I do send is a quarterly personal update about my life (work, family, what I'm reading), and it's the best relationship investment I make.
The Quarterly Personal Update: Email your network a short personal update every quarter on real work, real life and what you're into; nobody needs to reply.
Match Investment to Tier: Every touch costs different time and money, so spend dinners and gifts on your top tier and lighter touches on larger groups.
Social Media and Relationships: Marketing is one-to-many visibility and relationship building is one-to-few trust; social media belongs to the first and feeds the second, and you need both.
Be Worth Knowing: Share your own take and what you're into; industry jargon makes you invisible, while personality and stories make you memorable.