The link on page one contains info on the correct way to anneal cases. You do not want them to get red hot.
I'm not all that impressed with the tool. I like the idea of putting the bases in water, heating until the right temp is reached, and as you know, how much light is in the room will affect what you see as to color on the cases.
You do not want the body of the case anealed, only the neck.
It's your brass and rifle, but if you are going to do it, do a little research and do it right. There are kits that do one at a time which protects the base from the heat, I have never tried one, but it would be better than a tool that just turns the case while you play heat on the neck. Getting the neck too hot changes the grain structure of the metal. Why not just do it the right way???
Just my 2 cents, John K