I'll give this from the reverse perspective: as the School Overseer. I still believe that the TMS Guidebook is not a bad publication for anyone beginning to speak in public. The problem is that oftentimes the Overseers were not particularly good public speakers themselves--and often didn't understand what the book was saying--or how to give someone else counsel. But that's probably not unlike any local chapter of Toastmasters, is it? They did their best.
I too had a hard time giving negative counsel--especially when the person giving the talk was twice my age--and had enormous experience in public speaking. The toughest one came when a fellow elder's wife was being counseled on "Personal Appearance." Under the subheading "Proper Attire and Grooming," it has quite a lot to say about not dressing in a way that would draw attention to oneself, mentioning that women should exercise all due modesty. The elder's wife was certainly not the flashy sort. Very introverted and sweet. But she would ALWAYS wear a dress or skirt with a slit that HAD to rise to within an inch of her vagina. She would ALWAYS cross her legs in such a way as the main part of the dress or skirt would simply fall away under the table, exposing both of her legs in a way that (trust me) you're just not used to seeing on a Kingdom Hall stage. (They were pretty hot, by the way. Allow me a moment to calm down... (pause) Okay, I'm back.)
Anyway, during her entire talk, as I was looking over the info from the Guidebook, I began to get really nervous--because (y'know) I was supposed to be specifically counseling her on her appearance. How ON EARTH could I possibly tell her to cover her legs and thighs up more in front of the entire Kingdom Hall? I did EXACTLY as the other contributor mentioned: "Well it looks like we're running a bit short on time; we'll just give you your counsel after the meeting." Then I quickly went to another older elder for his suggestions. He just smiled, agreed that it was a difficult spot, and left it to me. She finally approached me, and asked very kindly if I was going to give her her counsel. I stared at her for about three seconds, debating what to do. Then I completely caved, saying, "Oh, I marked you "Good" on that Sister. Nice talk!"