I use 9.5 litre kegs and until I get some more kegs I force carb as there is nothing worse than needing a keg but there is still days to go with the at pouring pressure method. I have found that a slight change to the Ross method is spot on for me:- keg cooled to 3.5/4 degrees, 30psi through the gas post, rolling the keg back and forth with the gas post at the bottom for 50 seconds (stop watch). Gas off at bottle, continue rocking until pressure goes just below 20 psi, turn gas on and straight off again. The pressure is at 30psi, rock down to 20 psi again. Disconnect gas, keg in fridge to settle. When wanted release gas from keg, connect gas at pouring pressure and away you go. Have found this works every time.
Cheers