Most social advice assumes resources that a two-person business does not have. With four hours a week, the strategy has to be a shape rather than a checklist.
Pick one platform
Being adequate on four platforms is worse than being good on one. Choose based on where your customers already are, not where you find it easiest to post. For most local businesses that is Instagram or Facebook Groups; for most B2B it is LinkedIn; for anything visual and project-based it is Pinterest.
Two posts a week, forever
Not five for a month. Two, indefinitely. The compounding comes from duration, and duration is a function of sustainability.
Make the work the content
The cheapest content that works is documentation of what you already do. The process, the mistakes, the finished thing, the customer question you answered this week. It requires no ideation and it is more interesting than anything you would invent.
Geography is your edge
If you serve a place, local tags are the least competitive high-intent tags available. A national brand cannot outrank you on your own neighbourhood.
Reply to everything
At small scale this is genuinely feasible and it is the biggest advantage you have over larger competitors, who cannot. It builds the kind of relationship that produces recommendations, which is where small-business growth actually comes from.
Measure one number
Not reach. Enquiries, bookings or sales that mention finding you there. Everything else is a proxy, and proxies mislead when the numbers are small.