I have found flame color to be the most helpfull.
You don't want any glowing of the case. Not dull red, orange or any other color. In fact you don't even want the flame to change from blue to orange.
This video is an example of too much heat. Despite nothing "glowing".
This is a video of what you want the process to look like. Flame stays the same color, even color/heat ring around the neck and the base is cool to the touch after annealing.