Yes, you want to be very diligent and thorough, guiding the witness breadcrumb by breadcrumb through each and every separate point you make. You don't want to leave any holes in the logical chain for opposing counsel to take advantage of.

And you need to remember you're not only speaking to the people present in the courtroom at that moment but also potentially others in the future if the case is appealed. An appellate court's best resource to know what happened at trial is going to be the transcript. You need to be mindful that, even if you're talking to the witness and in that moment there's some nonverbal cue or some context that implies an answer without outright saying it, that won't appear on the transcript. That will be a big logical gap on the page, even if everyone in the courtroom at the moment knew the answer.

That's why sometimes you'll see if a witness, for example, nods yes in response to a question, the questioning attorney might say something like "please let the record show the witness is nodding in response to my question." The nod itself wouldn't appear on a transcript; it would just look like an unanswered question if the attorney moved on from that. So when you're questioning a witness, you have to make sure absolutely everything that you need to be said during their questioning is said, so you'll have ample evidence on the transcript and won't have to get into arguing about "oh well the witness said this and clearly meant that too, even if they didn't outright say it."

As for memorization, you're likely going to have been handling a case for at least several months and probably have put hundreds of hours of work into it by the time it goes to trial. At that point, you're hopefully going to have a pretty good handle on at least the basics. For finer points, you're absolutely allowed to bring notes with you to trial. You'd probably be foolish not to unless you had some savant-level memory. For important witnesses, you'd probably prepare at the very least a checklist of major points you want to hit while questioning them and read over that list multiple times before ever entering the courtroom. And even then you might have that checklist in front of you while asking questions just to make sure you didn't accidentally miss something you needed to talk about with that witness.