Preaching IS what moves them from one level of weak faith based upon deficient knowledge to the next level of stronger faith via the impartation of knowledge.
And if you're preaching Christ and His Kingdom, you're not preaching about food and drink. You're preaching righteousness, peace and joy in the Holy Ghost,
For the Kingdom of God is not a matter of what we eat or drink, but of living a life of goodness and peace and joy in the Holy Spirit.
In your life, if you love your brothers (Rom. 14:15), you will not make food and drink an issue. You won't trouble weaker brothers by preaching at them about it (Rom. 14:1) or insisting on taking your liberties. You will aim for harmony in the church. Not AT church. IN the church, the communion of saints.
19 So then, let us aim for harmony in the church and try to build each other up.
20 Don't tear apart the work of God over what you eat. Remember, all foods are acceptable, but it is wrong to eat something if it makes another person stumble.
21 It is better not to eat meat or drink wine or do anything else if it might cause another believer to stumble.
22 You may believe there's nothing wrong with what you are doing, but keep it between yourself and God. Blessed are those who don't feel guilty for doing something they have decided is right.
23 But if you have doubts about whether or not you should eat something, you are sinning if you go ahead and do it. For you are not following your convictions. If you do anything you believe is not right, you are sinning.