Yep,
As JKoravas said, the check valves only prevent flow when there is a pressure difference between the two. If the line pressure and the keg are in equilibrium, the beer is free to flow into the line if you lift/tip the keg such that it's higher than the hose during your force carbonation dance.
I typically connect my gas line to the *liquid in* post (by using the proper ball lock disconnect), and just rock the keg back and forth in the vertical position. It's more efficient, as the gas stream travels through the entire column of beer, being absorbed more readily with the increased contact time and surface area. ***You do have to be VERY careful to bring the headspace at the top of the keg to low pressure (pull the relief), and make sure that the gas line is pressurized before connecting it though.***