After I sanitize my keg I kick the lid back on and set the gasket. Then when you're ready to fill the keg pull the pressure relief valve and lock it open. Put a liquid coupler on the end of your racking cane and attach it to the keg. Using your spare CO2 line pressure your carboy to start the siphon. Now because your keg has already been purged with CO2 and you use CO2 to start the siphon you greatly reduce the risk of oxidizing your beer as you transfer. When you're done transferring, put that liquid coupler on your CO2 line and force carbonate down the liquid side.