Always be ready...

I've always read 1Peter 3:15 as a call to apologetics. "We've got to think our story through, so that when people ask us the tough questions we'll be ready!"
Colossians 4:6 is cross-referenced: "Let your speech always be with grace, as though seasoned with salt, so that you will know how you should respond to each person." Sounds like a call to take speaking lessons or to brush up on rhetoric, right?

Christ says in Luke 12 that “when they bring you to the synagogues and magistrates and authorities, do not worry about how or what you should answer, or what you should say. For the Holy Spirit will teach you in that very hour what you ought to say.”

This got me thinking: is this the difference between an evangelist and a teacher?
I've always thought of myself as more of a teacher than a preacher. I love to use words to tell truth, but not in that evangelistic sort of way. I used to think that it was simply a call to preach in a different way in order to reach a different sort of people; now I'm wondering about that.
Maybe the teacher is supposed to bear witness through teachings while the evangelist uses the witness of his or her own life.
I've always felt wrong giving on-the-spot testimony, because I'm never 100% sure of the words that I'm saying. I used to think that, given the time to sit down and think it through, I could probably write a pretty good evangelistic message for someone I might meet on the street. The message would be pithy, logical, and to-the-point; so it would appeal to some people more than others. It would not sound like personal testimony.
Now I see that I was wrong to compare these two styles of witness. Really, they're entirely different. I've also realized that it's irresponsible to assume that just because I'm exercising one side of my witness I'm okay to ignore the other side.
Paul was a teacher, right? His arguments are thorough and logical teachings that took a lot of work. But when I look at 1 Cor. 2, I see something very different. It's not that Paul ignored his teaching gift--his writing is still clear and logical, he's still saying these things in his letters for specific reasons. I suppose it's all rather obvious to some, but this is the first time I've really got the difference between the teacher and the witness, and it's the first time I've realized how important it is that both gifts can be active in one person. The Spirit can inspire me as a writer and as someone who has chance encounters with random people who need to hear a specific witness that I won't necessarily understand. (Question: how do I know if it worked?)

I started reading A.W. Tozer's Pursuit of God (which I bought at a library book sale in a beautiful old hardcover edition) a while back but put it down because it felt "too simple"; I think I should find out what he thinks about five-fold stuff.