I have seen competition shooters use an aquarium air pump to cool their rifle barrels by running a piece of tubing from the air pump to the bore. I would think the can of air is not going to do a whole lot for you unless you give a really good long blast. Maybe some of the competition shooters can chime in with an air pump technique.
Canned air is usually a liquid under pressure that expands into a gas. One byproduct from liquid->gas expansion is heat absorption. It will cool the barrel very rapidly. I would think that would be a bad thing in a precision rifle barrel but that is my uneducated opinion.
That is my point. The cooling would be dependant upon the length of the blast. I think, but have no data to back it up, that as long as we are not talking a radical temperature swing there would be no harm. Hence my point on doing this between rounds so there was no substantial heat build up in the barrel to begin with.