The importance of discerning and preaching according to the Holy Spirit’s purpose has not been emphasized in exegesis or in homiletics courses. Yet, nothing is more fundamental to solid biblical preaching.
III John can be preached either as one sermon or as a series of eight or nine sermons (I have done both), depending upon whether you preach the overall purposes or the sub-purposes. Of course, when you do the latter, you must never forget the general purpose that the specific purpose units were intended to support. That means they may not be preached in isolation but always in relationship to the larger thrust.
You are on the right track if you are prayerfully concerned and working at the problem. Stick to it, and in time things will get better. So, pastor, on behalf of your congregation, let me thank you for taking the time to consider an article like this! Now, to the matters at hand.
Dr. Adams has written some of the best work in the last 50 years on preaching that exists, and I was blessed to be able to sit under his preaching for a short while right before he retired. If you’re interested in being a preacher (or a better preacher if you are already!) start with these blog posts and then check out his books on homiletics from Timeless Texts.