I find wiping the tire with a gloved hand useful only for the psychological affect. I feel like I've done something useful.

Jobst Brandt points out the the glass in the tire will have hit the pavement at least 4 times by the time the wiper gets his hand on the first tire. To be affective you would have to start wiping before you hit the broken glass patch. Or you could use tire savers that wipe the tire all the time, if you don't mind the noise and the added resistance.

http://www.sheldonbrown.com/brandt/wiping.html

Sheldon Brown theorizes that it's possible that glass can get pushed further in on subsequent revolutions. Notice that both of these are just theories. I don't know of any scientific tests done on the nature of glass punctures.