For dimensions, in 2008, you can modify the dimension style so that it automatically includes a text mask.
(Dimension styles, text tab, fill color)
On most of our dwgs, though, we only use it for specific dimensions. Easiest way I've found to do that, is to change one, then paste properties. (Works for mtext too.) We usually throw a couple dims into the drawing, with the mask on, and then paste properties as we go.
I know there's got to be an easier way, but I don't know what it is.