Pressurize both kegs equally; run a jumper hose from the out to out connection. Disconnect the gas on the receiving keg, and then pull the release valve and bleed the beer over (while keeping source keg under pressure).
I do this all the time when I filter beer. You should have no problems especially of the beers are cold.
Leave the release out till the beer is near the top then close it off. The pressure from the other keg will be greater than the receiving keg. Once done, pressurize and pull the release once or twice to purge any o2.
I hook up 2 hoses.Set both kegs to 5psi, then hook up hoses, Gas to gas, beer to beer. Place source keg above recieving keg, then release pressure relief valve on recipient keg just until beer starts flowing , then let go. I read it somewhere and have done it this way ever since. Supposedly this keeps both keg at an equilized pressure and prevent foaming. If beer is cold you can tell where the beer leve is by the condensation on side of keg.