Question about blanketing a carboy or bottle with CO2

I have a 4 tap kegerator that I use with cornies.. Lately I have been wanting to experiment with fruit beers and fill some growlers. Mosher says you should blanket your carboy with CO2 to displace the oxygen before adding fruit.. I would assume you would also want to do this before filling a growler, but I also assume it's not 100% necessary-

ANYWAY, the question I have is what kind of mechanism do you use to blanket a carboy with CO2? What kind of connector would a guy need to add to his kegging system to be able to "squirt" CO2? Is there some kind of wand or "gun"? I know you can do this with a blichmann bottle filler, but I am not interested in purchasing one at this time.

Thanks for the help

all you need is a hose attached to a stopcock valve on your CO2 system (like the valves show in the pic below). Put the hose into the vessel, and open the valve for a little bit.