So I read the text a bit more carefully. Indeed, Acts 26 records Paul sharing his testimony. But it’s more than the three-fold model I was instructed to follow. Paul wove together a tapestry of his experiences, pre-evangelistic prompters, doctrinal elements, apologetic arguments, and even a call for a decision. While Agrippa did not respond as Paul had hoped (and prayed!—see his comment in verse 29), and accused Paul of losing his mind (v. 24), the king didn’t offer any dismissive, relativistic gibberish about “true for you but not for me.”
Note that the text calls Paul’s speech a “defense” (v. 1). That’s probably a better description than a “testimony,” and offering a defense is probably a better goal for us than merely sharing our story.