A deep well socket works. For the gas use a 12 point socket.
If you cant get them off with the socket wrench, a rubber mallet to impact the wrench may help. You also may have some residual sugar build up on the sockets. Fill the keg with some hot PBW (a gallon or 2 will do), let it sit upside down for a while, then try it again. This has helped me on some tough ones.