Yeah, the manual approach is time-consuming. We just built an internal tool to monitor keywords in specific subreddits and score posts (no FB group yet, not sure how hard to implement the monitoring). The tool runs every 6 hours and only shows posts with score higher than 70 and archives all other posts. We are still tweaking the tool to make it useful for ourself.
The monitor part is on the reddit public JSON API, like reddit.com/r/subredditname?q=keyword&sort=new&restrict_sr=on&feed=json. This way, we can see same results by doing search in Reddit directly.
One question, when you find these potential customers in Reddit threads and Facebook groups, what's your process after that? Are you responding directly in the groups, collecting leads to reach out to later, or something else? The reason for this question is that we are thinking to have automation to draft a reply if a post has a score higher than 85.