Consider also the possibility to fix default drawing settings including font
size :
In a drawing, if WITH NO SHAPE SELECTED you fix the font size, all
further shape or text you add to the drawing will use this size.
In other word if you select a command when a shape is selected the change
apply to the selection if nothing is selected it fix the default style
(font, thickness, filling, ...). Of course These settings can be saved in a
template.
Enjoy with visio.